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Videos uploaded by user “DoodleScience”
The Motor Effect | GCSE Physics | Doodle Science
 
01:37
GCSE Science Doodle Science teaches you high school physics in a less boring way in almost no time! Follow me: https://twitter.com/DoodleSci You can support me at: https://patreon.com/doodlescience Script: When a current passes through a wire it produces a magnetic field. If you put this magnetic field in another magnetic field, it puts a force on the wire. This is known as the motor effect. To determine the direction of the force you use a handy trick called Flemming's left hand rule. The way this works is by taking your left hand and making this shape with it. You then assign your first finger to the direction of the magnetic field, which is always north to south, your second finger to the direction of the current, and your thumb to the direction of the force. For example, in this case, Flemming's left hand rule states that the force would act in this direction. A simple electric motor works using this fact. It works by looping a coil of wire around to two electrical contacts inside a magnetic field. This causes one side of the wire to move up and the other part to move down, which causes the whole thing to spin. It is attached to something called a split ring commutator which is a clever way of swapping the contacts every half turn to keep it moving in the same direction. You can make the motor go faster by either increasing the current or by using a stronger magnetic field. So next time you use your hair dryer, you’ll know something more about the way it spins. References: 1. http://www.bbc.co.uk/education/subjects/zrkw2hv 2. CGP GCSE Physics AQA Revision Guide.
Views: 45786 DoodleScience
Moments | GCSE Physics | Doodle Science
 
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GCSE Science Doodle Science teaches you high school physics, in a less boring way, in almost no time! Follow me: https://twitter.com/DoodleSci You can support me at: https://patreon.com/doodlescience Script: A moment is the turning effect of a force. It’s calculated by multiplying the force by the perpendicular distance between the force and the pivot. For example, by turning a spanner you are producing a moment. If you apply a force of 15N to the end of the spanner and the length of it is 0.1m, then the moment you are applying is 1.5Nm. However you can apply a force that is not perpendicular, in which case the distance is not the length of the spanner but is the distance from the line of action of the force to the pivot. This will produce a smaller moment, so to produce the maximum moment, you need to apply force at 90 degrees. Moments are often referred to as force multipliers because they reduce the force needed to perform certain tasks. You’ve probably all experienced this at some point in your lives but haven’t realised the reason why. Using a wheelbarrow is an example of a lever being used to reduce the effort necessary to lift the load. It works using the concept of balanced moments. An object is balanced when the sum of the clockwise moments about a pivot are equal to the sum of the anticlockwise moments about the same pivot. For example, if a force of 300N is applied 2m from the pivot, and another force of 700N is applied on the other side of the pivot then it must be applied 0.86m from the pivot in order for the moments to balance. This means that you can apply small forces at further distances to achieve much greater forces on the other side. Which is why you’ll find it much easier to close your door from the handle rather than near the hinges. References: 1. http://www.bbc.co.uk/education/subjects/zrkw2hv 2. CGP GCSE Physics AQA Revision Guide.
Views: 51582 DoodleScience
Transformers | GCSE Physics | Doodle Science
 
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GCSE Science Doodle Science teaches you high school physics in a less boring way in almost no time! Follow me: https://twitter.com/DoodleSci You can support me at: https://patreon.com/doodlescience Script: Transformers change the potential difference of electricity. There are two main types of transformer that are used in the national grid. These are step up and step down transformers. Each of them consists of a two coils of wires around an iron core. In a step up transformer, the voltage is increased and the primary coil has fewer turns of the wire than the secondary coil. In a step down transformer, the voltage is decreased and the primary coil has more turns that the secondary coil. The way it works is by electromagnetic induction, and it only works with an a.c. current. The current passes into the primary coil, which produces an alternating magnetic field in the iron core. The magnetic field is constantly changing direction 100 times per second if the frequency of the a.c. current is 50Hz. This alternating magnetic field induces a potential difference across the secondary coil at the same frequency as the primary coil. Depending on whether it is a step up or step down transformer, the potential difference will be greater or lower across the secondary coil compared to the primary. There is a formula you can use to work out what the potential difference across the coils will be. It is p.d across primary coil/p.d across secondary coil = number of turns on primary coil/ number of turns on secondary coil. For example, a transformer has 100 turns on the primary coil and 2000 turns on the secondary. If the input p.d. is 500V, then the output p.d. can be calculated by rearranging the formula to give 10000V. Transformers are almost 100% efficient so we can assume that the power that goes into them also comes out. This gives us another handy formula, which is, the current in the primary coil x the p.d across it = the current in the second coil x the p.d. across it. For example, the current of 2A is supplied to the primary coil of a transformer with a p.d. of 300V across it. The secondary coil has a 15A current flowing though it. By rearranging the equation we can work out the p.d. across the secondary coil as being 40V. There is another type of transformer called a switch mode transformer. These are the ones you get in your laptop and mobile phone chargers. They operate at very high frequencies between 50 and 200 kHz. They also use very little power when your laptop or mobile phone is not plugged in. Which is good for when you accidentally leave your charger in the socket. References: 1. http://www.bbc.co.uk/education/subjects/zrkw2hv 2. CGP GCSE Physics AQA Revision Guide.
Views: 34905 DoodleScience
Life Cycle of Stars | GCSE Physics | Doodle Science
 
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Follow me!: https://twitter.com/DoodleSci Doodle Science teaches you high school physics in a less boring way in almost no time! GCSE Science Script: Stars initially form from clouds of dust and gas. The force of gravity makes the gas and dust spiral in together to form a protostar. As the gas and dust falls together, it gets hot. A star forms when it is hot enough to fuse hydrogen nuclei into to helium. The star then immediately enters a long stable period, where the heat created by the nuclear fusion provides an outward pressure to counteract the force of gravity pulling everything inwards. In this stable period it’s called a main sequence star and it lasts several billion years. Luckily for us our sun in about half way through it’s stable period. Eventually however, like everything, the star must die. It takes one of 2 courses, the boring way or the cool way. Stars that are about the same size as our sun tend to take the boring way out. When the hydrogen begins to run out they begin to fuse heavier elements all the way up to iron in its core. The star at this point swells into a red giant which is unstable and ejects it’s outer layer of dust and gas as a planetary nebula; leaving behind a hot dense solid core called a white dwarf. Told you it was boring. Stars much bigger than our sun such as Betelgeuse are big enough to take the much more interesting route. Once they run out of hydrogen they start to swell up too, into a red super giant. At this point they are making elements in their core up to iron but it’s when they explode in a supernova, that the heavier elements are formed that are found all over our planet. The exploding supernova throws out its outer layers of dust and gas into space leaving a very dense core called a neutron star or in some cases a black hole. So if stars are responsible for nearly all of the elements on the periodic table, I guess you could say this video was brought to you by stars.
Views: 35694 DoodleScience
Centre of Mass | GCSE Physics | Doodle Science
 
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GCSE Science Doodle Science teaches you high school physics in a less boring way in almost no time! Follow me: https://twitter.com/DoodleSci You can support me at: https://patreon.com/doodlescience Script: The centre of mass of an object is the point where the entire weight of an object appears to act. Working out the centre of mass of a symmetrical object is easy; it’s simply the point where the lines of symmetry cross. However it’s very unlikely that you’ll be dealing with such perfect shapes so you work it out by suspending the object freely, along with a plumb line. The centre of mass is always below the point of suspension, so by marking the vertical along the plumb line you know the centre of mass is somewhere along that line. By suspending the object from another point and repeating the process, you get two lines that intersect and the point of intersection is the centre of mass. The position of the centre of mass is very important when it comes to the stability of an object. For example, a double decker bus is built to have a very low centre of mass and a wide base so that the line of action of its weight stays within the base when it goes around a sharp corner. If something has a high centre of mass combined with a small base then it is very unstable and will topple over with minimal effort. A plumb line is an example of a simple pendulum. All it consists of is a weight attached to a piece of string that can swing freely. The time taken for it to swing from one side to the other and back again is called the time period. The time period of a pendulum of the same length is always the same no matter what height you release it from, which is what makes them so good at keeping time. The time period and the frequency are related by the formula: T = 1/f. So if a pirate ship at a theme park swung with a frequency of 0.2Hz then the time period would be 5s, which is one scary ride! References: 1. http://www.bbc.co.uk/education/subjects/zrkw2hv 2. CGP GCSE Physics AQA Revision Guide.
Views: 28918 DoodleScience
Gravitational Fields | A-Level Physics | Doodle Science
 
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A Level Physics Doodle Science teaches you high school and College physics in a less boring way in almost no time! Follow me: https://twitter.com/DoodleSci You can support me at: https://patreon.com/doodlescience Script: A gravitational field is a region around one mass, which affects other nearby masses. It is very weak however which is why the effect is only significant on large objects like the Earth. We can represent the Earth’s gravitational field by drawing field lines showing the direction of the gravitational force on masses in the field. In this case the field is radial and equally spread around the earth. On the surface of the earth the gravitational field is approximately uniform because the field lines are virtually pointing in the same direction and are equally spaced. This is why we assume the acceleration due to gravity is a constant of 9.81m/s^2 because the change at small vertical heights is negligible. Newton’s law of gravitation states that all masses attract each other with a force that is proportional to the product of their masses and inversely proportional to the square of the distance between the two centres of mass. This gives us the equation F= - GMm/r^2. Where G is the universal gravitational constant of 6.67x10^-11; M is the mass of the larger body; m is the mass of the smaller body; and r is the distance between the centres of mass of the two bodies. The minus sign simply refers to the to the fact that the force is attractive. For example, two bodies, one of mass 6kg and the other of mass 20kg are placed 50cm apart. From this we can work out the gravitational force acting on each object as 3.20x10^-8N. The force acting on each body is equal because they are attracted to each other. The gravitational field strength is the force per unit mass at a point in a gravitational field. For a uniform field the equation is F/m, where F is the force experienced by the body and m is the mass of the body. For a radial field, the gravitational field strength obeys an inverse square law. The equation for it is g=GM/r^2. You can see how the gravitational field strength would decrease the further you were from the centre of the body producing the field. This formula can be used to work out the masses of celestial bodies. For example, given that the gravitational field strength on the earth’s surface is 9.81 N/kg and the radius of the earth is 6400km, we can work out the mass of the earth to be 6.02x10^24kg. When considering planetary motion, the gravitational force acting on the body orbiting is equal to the centripetal force because the force acts perpendicular to the direction of motion. By equating the two formulas and using the formula for the speed of an object in circular motion we get the equation T^2=(4π^2/GM)r^3. Where T is the orbital period in seconds and r is the distance between the centres of mass of the orbiting body and body being orbited. This equation shows Kepler’s third law which states that the T^2 is directly proportional to r^3. This also suggests that for a set of celestial bodies (e.g. the planets of our solar system) orbiting the same large body (e.g. the sun), T^2/r^3 is a constant and is equal for all the celestial bodies. For example, given that it takes 365 days for the Earth to orbit the sun and that the distance of the earth from the centre of the sun is 1.5x10^11m. We can work out the mass of the sun to be about 2.00x10^30kg. Given that the orbital period of mars is 687 days, we can use the Earth’s orbital characteristics to work how far Mars is from the centre of the Sun as being 2.29x10^11m. A geostationary orbit is an orbit around the Earth whose orbital period is 24 hours. They are located above the equator and are always vertically above the same point on the surface of the Earth. This makes them useful for TV satellites because the dishes can be pointed to a fixed point in the sky. Which is quite convenient I’d say. References: 1. CGP AS & A2 Physics for OCR A, ISBN: 9781847624192
Views: 45213 DoodleScience
Circular Motion | GCSE Physics | Doodle Science
 
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GCSE Science Doodle Science teaches you high school physics in a less boring way in almost no time! Follow me: https://twitter.com/DoodleSci You can support me at: https://patreon.com/doodlescience Script: Circular motion is quite self-explanatory really; it’s simply the physics behind things moving in circles. When something moves in a circle it’s velocity is constantly changing, even if its speed is constant. This is because velocity is both speed and direction. So since the direction is constantly changing, its velocity is also constantly changing and so the object must be accelerating; and this acceleration is towards the centre of the circle. If there is acceleration, this there must be a force producing it; and this resultant force is called the centripetal force and also acts towards the centre of the circle. A car going around a bend is an example of circular motion. The friction between the car’s tyres and the road produces the centripetal force. Without the friction, the car would fly off at a tangent. Another example of circular motion is how the moon orbits the Earth. The gravitational attraction between the moon and the earth is the centripetal force. The magnitude of the centripetal force depends on the speed, mass and the radius of the circle the object is travelling around. The faster the object is moving, the greater the centripetal force has to be to keep it in circular motion. An object of grater mass also needs a greater centripetal force to keep it moving in a circle. And if the object is moving in a smaller circle, the centripetal force has to be bigger because the object is effectively changing direction more quickly and therefore needs a greater force to produce a greater acceleration. Hopefully that helped you get your head around it (pun intended). References: 1. http://www.bbc.co.uk/education/subjects/zrkw2hv 2. CGP GCSE Physics AQA Revision Guide.
Views: 15086 DoodleScience
Electromagnets and Electromagnetic Induction | GCSE Physics | Doodle Science
 
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GCSE Science Doodle Science teaches you high school physics in a less boring way in almost no time! Follow me: https://twitter.com/DoodleSci You can support me at: https://patreon.com/doodlescience Script: When a current flows through a wire it causes a magnetic field to be produced around the wire. For a single piece of wire, the magnetic field is made up of concentric circles around the centre. If you coil the wire up however, the magnetic field acts a lot like a standard bar magnet. The wire is usually wrapped around an iron cylinder, which increases the strength of the electromagnet. The useful thing about electromagnets is that they can be switched off. As soon as there is no current flowing through the wire, there is no magnetic field. That makes them handy for picking up heavy cars in a scrap yard and still being able to let them go. Just as a current can create a magnetic field. A magnet can create a current. This process is called electromagnetic induction. It works when a changing magnetic field produces a potential difference across a conductor, such as a wire. The way you do this is by moving a wire through a magnetic field back and forth repeatedly. As you move it one way it produces a potential difference, which is positive, and when you move it back, the p.d. is negative. This keeps alternating constantly, which is how you produce an alternating current. This is how generators work, except they get around the back and forth movement of the wire by having a magnet in the middle of a coil of wire that can spin. As the magnet spins, its polarity will swap every half turn, this will cause the p.d. across the wire to alternate every half turn and produce an alternating current to power our homes. References: 1. http://www.bbc.co.uk/education/subjects/zrkw2hv 2. CGP GCSE Physics AQA Revision Guide.
Views: 43433 DoodleScience
Hydraulics | GCSE Physics | Doodle Science
 
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GCSE Science Doodle Science teaches you high school physics in a less boring way in almost no time! Follow me: https://twitter.com/DoodleSci You can support me at: https://patreon.com/doodlescience Script: Hydraulics might sound complicated but all they are, is another force multiplier. They utilise the fact that liquids are virtually incompressible, which means when you compress them, the pressure you apply to one point of the liquid is transmitted equally in all directions. For example if you have a balloon with a few holes in it and you squeeze the top of the balloon, the water will squirt out of all of the holes. This shows that the pressure applied at the top of the balloon must have been transmitted equally to all other parts of the liquid. In order to work with hydraulics, the equation Pressure = Force/ Cross sectional area is needed. Where pressure is measured in Pascals, force in newtons and the cross sectional area in square metres. A hydraulic system works by applying a small force to one piston to produce a much larger force to a second piston. For example, if one piston has a cross sectional area of 0.001m^2 and a force of 15N is applied to it, then since the pressure is transmitted equally to the other piston of area 0.01m^2 then the force acting on the second piston is 150N Hydraulic systems are used in all kinds of things such as car braking systems, car jacks and on the landing gear of some aircraft. All these applications take a small effort force and produce a large load. And it’s a good job too, because I wouldn’t want to change a tyre without hydraulics. References: 1. http://www.bbc.co.uk/education/subjects/zrkw2hv 2. CGP GCSE Physics AQA Revision Guide.
Views: 18420 DoodleScience
Hooke's Law | GCSE Physics | Doodle Science
 
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Follow me!: https://twitter.com/DoodleSci Doodle Science teaches you high school physics in a less boring way in almost no time! Script: Elastic objects (such as a spring) can store elastic potential energy when they are stretched. For example this happens when a catapult is stretched back. When an elastic object -- such as a spring -- is stretched, the increased length is called an extension. The extension of a truly elastic object (again, such as a spring) is directly proportional to the force applied, provided the limit of proportionality is not exceeded. Meaning the object being stretched doesn't become permanently deformed, such as when a spring doesn't return to its original position after the load is removed. This proportionality is called Hooke's Law and the Force is equal to the spring constant times the extension. The spring constant is measured in N/m and is different for different objects and materials. You work it out by carrying out an experiment with an elastic object and adding a load or force to it. You then measure the extension of the spring and sub the numbers into the formula to get the spring constant. The greater the value of k, the stiffer the spring.
Views: 68055 DoodleScience
Transverse and Longitudinal Waves | GCSE Physics | Doodle Science
 
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Follow me!: https://twitter.com/DoodleSci Doodle Science teaches you high school physics in a less boring way in almost no time! Script: Waves are vibrations that transfer energy from place to place without matter being transferred. Think of a Mexican wave in a football crowd: the wave moves around the stadium, while each spectator stays in their seat only moving up then down when it's their turn. There are two types of waves, transverse and longitudinal. In transverse waves, the oscillations are at right angles to the direction of the energy transfer. Light and other types of electromagnetic radiation are transverse waves. In longitudinal waves, the oscillations are parallel to the direction of the energy transfer. Sound waves are longitudinal waves. These waves show areas of compression and rarefaction, the areas of compression are where the parts of the wave are close together, while the areas of rarefaction are where they are far apart. Waves have an amplitude, a wavelength and a frequency. The amplitude of a wave is its maximum disturbance from its undisturbed position. Which basically means the distance between the middle and it's highest point. The wavelength of a wave is the distance between a point on one wave and the same point on the next wave. And the frequency is the number of waves that pass a certain point each second. The unit of frequency is measured in hertz, but it's also measured in kilohertz, megahertz and gigahertz for very high frequencies. The speed of a wave is related to its frequency and wavelength, according to this equation: v=f x (lambda) where v is the wave speed in metres per second, f is the frequency in hertz and (lambda) is the wavelength in metres. For example, a wave with a frequency of 100 Hz and a wavelength of 2 m travels at 200 m/s. But that's nothing compared to light's 299 792 458 m/s. That's pretty damn fast.
Views: 74225 DoodleScience
Charge, Current and Voltage | GCSE Physics | Doodle Science
 
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Follow me!: https://twitter.com/DoodleSci Doodle Science teaches you high school physics in a less boring way in almost no time! Script: There are three things to understand when we talk about electricity: Charge, Current and Voltage. All objects and materials have charge; it's created by the net of electrons or protons. If there are more electrons, the substance will be negatively charged and if there are more protons, it will be positively charged. When a non-conductive substance such as plastic gets a charge by having electrons transferred to it, it creates a static electric charge. Such as when you rub a balloon on your head and it sticks or when you put your hand on a Van Der Graff. Charge is measured in Coulombs and 1 coulomb is equal to the charge of approximately 6.241x1018 electrons. Now the movement of this charge is called current and it's best to think of it as a river. Just as we measure the amount of water passing a point every second, current is the amount of coulombs passing a point every second. To measure it, we can put an ammeter in place to tell us how many coulombs are passing that point each second. But because physicists and engineers use this measurement so much, they decided to give is a name called an ampere or Amp. Voltage or potential difference is a bit trickier to understand. The way I like to visualize it is by thinking of a lake that is completely still and therefore has no current. If we were to tilt the lake on its side, the water would rush from the higher gravitational potential to the lower. It's the same concept with Voltage, only instead of gravitational potential difference; we give it an electrical potential difference. We do this by using a battery for example, the battery gives one side of a wire more electric potential energy than the other side, so the current travels through the wire. The more potential difference we give it, the faster the current flows. Just as a steeper waterfall causes water to fall quicker. But why do we call it potential? Because it is the potential to do work. The unit for the potential to do work is given in Joules per Coulomb and 1 of these is the same as 1 Volt because people decided to give it a name. Lets think of a 1.5V battery connected to a light bulb. What does the 1.5V mean? Well it means if 1 coulomb were to come out of one end of the battery, it could transfer 1.5J of light and heat before it entered the other side again.
Views: 62345 DoodleScience
Simple Harmonic Motion | A-Level Physics | Doodle Science
 
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A Level Physics Doodle Science teaches you GCSE and A Level physics in a less boring way in almost no time! Follow me: https://twitter.com/DoodleSci You can support me at: https://patreon.com/doodlescience References: 1. CGP AS & A2 Physics for OCR A, ISBN: 9781847624192
Views: 24220 DoodleScience
Resultant Forces | GCSE Physics | Doodle Science
 
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Follow me!: https://twitter.com/DoodleSci Doodle Science teaches you high school physics in a less boring way in almost no time! Script: An object may have several different forces acting on it, which can have different strengths and directions. But they can be added together to give the resultant force. This is a single force that has the same effect on the object as all the individual forces acting together. For example a rocket travelling into space with a thrust of 1000N and a weight of 200N will begin to accelerate because the resultant force is 800N. When all forces are balanced, the resultant force is zero. In this case: A stationary object remains stationary and a moving object keeps on moving at the same speed and in the same direction. For example, in a tug-of-war competition, the resultant force when in a stalemate is zero, because both teams are pulling on the rope with equal force. In this case the result is stationary. However, when a skydiver jumps out of a plane, his weight is greater than the air resistance at first and he starts to accelerate. He then reaches a point where his weight and air resistance balance out, this is called terminal velocity and the resultant force is zero, but don't worry, he's not stationary of course, he's just plummeting to the ground at a constant speed that's all.
Views: 46937 DoodleScience
Nuclear Fission and Fusion | GCSE Physics | Doodle Science
 
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Follow me!: https://twitter.com/DoodleSci Doodle Science teaches you high school physics in a less boring way in almost no time! GCSE Science Script: Nuclear power plants generate energy in today’s world by using nuclear fission. Fission is just another word for splitting. So the process of splitting a nucleus is called nuclear fission. For fission to be done in any practical way we have to use big atoms like uranium or plutonium. To start off the process, one of these isotopes must absorb a neutron. When this happens, the nucleus becomes unstable and splits into two smaller nuclei. Two or three neutrons are also released in the process, which can go on to cause a chain reaction. A lot of energy is released during nuclear fission and I mean A LOT. You could meet the demand of an average American every year with just 275g of natural uranium. That’s the equivalent to burning 4.4 tonnes of coal! Nuclear fusion as you probably guessed is the opposite of nuclear fission as you fuse atoms together instead of splitting them up. In fusion we use the smallest atoms we can get because it doesn’t require as much energy as bigger atoms would to fuse. Specifically the isotopes hydrogen-1 and hydrogen-2. We create conditions that forces these atoms to be squashed so closely that they fuse into Helium-3 and releases about 3-4 times more energy than a fission reaction. I’ll leave you to calculate the equivalent in coal.
Views: 55579 DoodleScience
Circular Motion | A-Level Physics | Doodle Science
 
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A Level Physics Doodle Science teaches you high school and College physics in a less boring way in almost no time! Follow me: https://twitter.com/DoodleSci You can support me at: https://patreon.com/doodlescience Script: Circular motion is simply the physics of things moving in circles. This happens all the time, for example you are moving in a circle around the earth as it rotates about its axis. If you are on the equator you would be moving through a larger circle per day than if you were in London, which is much further north. However, both of these places would have the same angular displacement at any point in the day. The angular displacement is measured in radians rather than degrees because it makes calculations much more straightforward. For example, the distance you move along the circle is given by the formula s = r θ. Where s is the arc length in metres, r is the radius of the circle in metres and θ is the angular displacement in radians. There are 2π radians in a circle, which means that 2π = 360 degrees and using this fact we can convert between degrees and radians. For example, an aeroplane performing a loop de loop of radius 60m turns through 135 degrees. To calculate the distance the plane has moved we have to first convert the degrees into radians. This is done by dividing 2π/360 to get the radians for 1 degree and multiplying it by 135, which gives ¾ π or 2.36 radians. This can then be used to work out the distance the plane has travelled as being 141m. When an object undergoes circular motion, the object will move at a constant speed but changing velocity. The velocity is changing because the direction is constantly changing and velocity is both speed and direction. This means that there is an acceleration, called the centripetal acceleration. The formula for this is a = v^2/r, where v is the velocity and r is the radius. Another relationship in circular motion is ω = v/r, where ω is the angular speed, which is a measrure of how many radians are being turned through per second and it is measured in rad/s. Another formula for ω is 2π/T where T is the time period of one complete rotation measured in seconds. A centripetal force must be occuring here in order to produce this acceleration. The formula for centripetal force is F = mv^2/r. Where m is the mass of the body undergoing circular motion, v is the velocity and r is the radius of the circle. For example, another aircraft display team perform a horizontal circle of radius 350m travelling at 100m/s. From this we can work out the angular speed as being 0.286 rad/s. If the mass of the pilot was 75kg, then we could work out the centripetal force as being 2140N. It’s important to determine which forces are directed towards and away from the centre of the circle in order to determine the resultant force which is equal to the centripetal force. For example going back to the loop de loop performed by the aircraft, there are 2 points in the stunt that are of interest, at the top and at the bottom of the circle. At the top, the normal reaction force of the pilot from his seat and his weight are both acting downwards, towards the centre of the circle. At the bottom of the circle, the normal reaction force acts up towards the centre of the circle and the weight acts down. Given that the pilot had a mass of 80kg and the plane was travelling at 100m/s we can work out the normal reaction force on the pilot at the bottom of the circle to be 14100N and at the top the normal reaction force as 12500N which is a very strong force. References: 1. CGP AS & A2 Physics for OCR A, ISBN: 9781847624192
Views: 89454 DoodleScience
Gravitational Potential and Kinetic Energy | GCSE Physics | Doodle Science
 
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Follow me!: https://twitter.com/DoodleSci Doodle Science teaches you high school physics in a less boring way in almost no time! Script: Gravitational potential energy is the energy stored in an object as the result of its vertical position or height. The energy is stored as the result of the gravitational attraction of the Earth and the object. The gravitational potential energy of the massive ball of a demolition machine is dependent on two variables - the mass of the ball and the height to which it is raised. These variables are related and can be expressed by the following equation: Ep = m x g x h. Where Ep is the Gravitational potential energy in Joules. M is the mass in kilograms. G is the gravitational field strength in Newton's per kilogram and H is the change in height in metres. To determine the gravitational potential energy of an object, a zero height position must first be arbitrarily assigned. Typically, the ground is considered to be a position of zero height. But this is merely an arbitrarily assigned position that most people agree upon. So if someone were to go to the top of Mount Everest, they would have a higher gravitational potential energy than if someone were to stay on the beach. If he were 85kg, then his gravitational energy would be the height of Mount Everest, which is 8,848m times by 85 times by 9.8N/kg which is the pull of gravity from the earth. So the gravitational potential energy of this guy is 7 370 384 Joules. But this energy is just potential, if he were to jump off the peak of Mount Everest then most of the potential energy will be transferred to kinetic energy. We can calculate his kinetic energy with the equation: Ek = ½ × mass × velocity2. If he was travelling at a velocity of 54m/s; then his Kinetic energy would be 123 930 Joules. But some of it will be lost as heat as well. This is why a pendulum on a clock eventually stops because a small percentage of energy is being lost as heat with every tick.
Views: 65904 DoodleScience
Eye vs Camera | GCSE Physics | Doodle Science
 
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Follow me!: https://twitter.com/DoodleSci Doodle Science teaches you high school physics in a less boring way in almost no time! GCSE Science Script: The eye is a combination of smaller parts which give you the ability to be watching this video right now. It’s made up of 8 main parts; at the front is the cornea. This refracts light by a fixed amount to help us focus the light. The pupil is simply the hole where the light enters the eye and the size of this hole is controlled by the iris. Once the light gets in, it’s refracted further by the lens, which can be adjusted to refract more or less in a process called accommodation. When an object is near the ciliary muscles contract to make the lens more curved. This causes the suspensory ligaments to slacken and the light focuses directly onto the retina, which processes the light and triggers electrical impulses to be sent to the brain through the optical nerve. If the object is far away the opposite occurs. The ciliary muscles relax and the suspensory ligaments stretch, causing the lens to flatten out in order to focus the light correctly. Cameras are designed very similarly to the eye, probably because of how efficient it is. To focus the light it uses a converging lens, which is adjusted by bringing the lens closer or further away from the film or charge-coupled device. This part isn’t the same as the eye because the glass lens only has a constant shape. The aperture of the camera adjusts size to control how much light enters it, which is very similar to the iris and pupil. As I mentioned earlier the film or charge-coupled device detects the light and converts them to electrical signals, very similar to the retina. Although the resolution of cameras are extremely high and they can capture video at very high frame rates, I think the eye takes the lead as it’s an amazing feat of evolution.
Views: 24645 DoodleScience
Distance-Time and Velocity-Time Graphs | GCSE Physics | Doodle Science
 
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Follow me!: https://twitter.com/DoodleSci Doodle Science teaches you high school physics in a less boring way in almost no time! Script: When were talking about motion, it can be very useful to draw a graph. If you're moving in a straight line, a graph that's useful is a distance-time graph; this is where you have distance on the Y-axis and time on the X. If we mark this as the starting point and start walking at a steady speed of 2m/s, then we can plot this on the graph and draw a straight line between the points. If we decide to stop the line would be flat, then if we return to our original position the line slopes back to the origin of the graph. You can use the steepness of the slopes to work out your speed. If the line is very steep then you're moving fast but if you're moving slowly then the graph will have a gentler slope. You can then use the numbers on the axis to work out the actual speed you were traveling. The equation for speed is distance over time, so all you have to do is read the numbers, if you travelled 20m in 5 seconds then your speed will be 4m/s. If you want to work out how fast an apple falls to the ground then a distance-time graph won't do because the pull of gravity causes it to accelerate. Instead we can use a velocity time graph. In this case the slope of the graph tells us that an object is accelerating. If the line is straight then the acceleration is constant and if it's curved then the acceleration is changing. You can work out the acceleration of an object by dividing the change in velocity by the time it took to fall. If the graph shows a straight horizontal line, the object is travelling at a constant speed. When the graph starts to slope back to the origin, it means the object is decelerating. For instance when the apple hits the floor, the graph would show a very steep line. You can also find the distance you've travelled by working out the area under the graph. It's as easy as working out the areas of squares, triangles and trapeziums and hence how far you've travelled.
Views: 110097 DoodleScience
Resistance | GCSE Physics | Doodle Science
 
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Follow me!: https://twitter.com/DoodleSci Doodle Science teaches you high school physics in a less boring way in almost no time! Script: An electric current flows when electrons move through a conductor, such as a metal wire. The moving electrons can collide with the ions in the metal. This makes it more difficult for the current to flow, and causes resistance. The length of a wire and its thickness affect the resistance in the circuit. The longer the wire, the greater the resistance because electrons collide with ions more often. The resistance of a thin wire is greater than the resistance of a thick wire because thin wire has fewer electrons to carry the current. Resistance can be found by measuring the current flowing through it, and the voltage across it. The equation for resistance is R = V/I where R is measured in Ohms, V in Volts and I in Amps. We can plot these readings on a graph to show how the voltage varies with the current. The current flowing through a fixed resistor is directly proportional to the voltage across is. This is shown by a straight line on a graph. The resistance in a filament bulb is not consistent such as in the fixed resistor. The resistance of the lamp increases as the temperature of its filament increases. The current flowing through a filament lamp is not directly proportional to the voltage across it. The graph in this case would look more like an S shape. The reason for the increase in resistance is because as the temperature increases, the metal ions vibrate more, therefore there will be more collisions with the flowing electrons and so more resistance.
Views: 16669 DoodleScience
Heat Transfer - Radiation | GCSE Physics | Doodle Science
 
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I'm going to be covering the entire AQA GCSE physics course this way. So, if you have any questions about it, leave a comment and I will reply to it as soon as possible. Thanks for watching! Script: Heat can be transferred from place to place by conduction, convection and radiation. Today though we'll be focusing on radiation. All objects emit and absorb thermal radiation, which is also called infrared radiation. Even we do, just a very low amount, but it can still be picked up by thermal imaging cameras that detect the infrared radiation and convert it to visible light. Like this picture of a hair dryer. The hotter an object is, the more radiation it emits, some of it even becomes visible light that we can see. Infrared radiation is a type of electromagnetic radiation, which has a lower frequency than light and involves waves rather than particles. This means that, unlike conduction and convection, radiation can even pass through the vacuum of space. This is why we can still feel the heat of the Sun, even though it's 150 million km away from the Earth. Some surfaces are better than others at emitting and absorbing infrared radiation. Dark, Matt surfaces are good at emitting and absorbing infrared radiation, which is why solar panels are black in order to absorb the maximum amount heat for your hot shower, while light, shiny surfaces are poor at absorbing and emitting infrared radiation but they ARE good reflectors. Which is how thermos' work, if you want to keep your cup of tea hot all day, you put it in a thermos that is coated inside with a shiny surface to reflect the radiation back to the tea. Or if you don't have one, just wrap it in some tin foil.
Views: 112714 DoodleScience
Converging Lenses | GCSE Physics | Doodle Science
 
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Follow me!: https://twitter.com/DoodleSci Doodle Science teaches you high school physics in a less boring way in almost no time! GCSE Science Script: A lens is a piece of transparent material, like glass, that uses refraction to form an image by changing the direction of light. There are two types of lens; converging and diverging. Converging lenses are shown using this symbol. The lenses curve out on both sides. A ray diagram can be drawn to show the refraction of light through the lens. Light rays that travel through them produce a real image as they all meet at the same point, called the principle focus. The distance between the centre of the lens and this point is called the focal length. Ray diagrams can be drawn to show how a certain lens will form an image. They follow a set of tedious steps so bear with me. Firstly, a principle axis is drawn through the middle of the lens and the object is placed with its base touching the line, usually represented as an arrow. You then draw two rays from the tip of the object. One passing parallel to the principle axis and then through the principle focus. The other is a straight line through the centre of the lens. The point where the rays meet is the tip of the object’s image. Ray diagrams allow us to work out whether the image will be magnified or diminished, upright or inverted and real or virtual. The image you see through a magnifying glass is magnified (funnily enough), upright and virtual, because it’s on the same side as the object. This happens to converging lenses when the object is placed between the lens and the principle focus. You can work out the factor of magnifications by dividing the image height by the object height. For example, the image here appears to be 75cm high when viewed through the magnifying glass but the object is only 25cm. This means the magnification is 3 times bigger than the original object.
Views: 12394 DoodleScience
Heat and Thermodynamics | A-Level Physics | Doodle Science
 
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A Level Physics Doodle Science teaches you GCSE and A Level physics in a less boring way in almost no time! Follow me: https://twitter.com/DoodleSci You can support me at: https://patreon.com/doodlescience Script: Everything, whether it’s a solid, liquid or gas, has energy. The only difference between these states of matter is the amount of energy they have. This energy comes in two forms within the substance, kinetic energy and potential energy. The kinetic energy is from the movement of the particles within the mass. You can visualise the potential energy as if there were springs between the particles in a solid, which forces them to vibrate about their fixed positions. The sum of the randomly distributed potential energy and kinetic energy of the particles in the system is called the internal energy. Heat always moves from a region of higher temperature to a region of lower temperature. This will continue to flow until both bodies have the same temperature. At this point it is said to be in thermal equilibrium. There are three ways in which heat is transferred. These are conduction, convection and radiation. Conduction is the transfer of heat by neighboring atoms vibrating against each other and is the most common method of heat transfer between solids. Convection is the transfer of heat from one place to another by the movement of a liquid or a gas. As the particles gain heat they spread out, become less dense and rise above the colder air causing the colder air to sink, this is how a radiator (despite the name) heats up your room. Radiation is the transfer of heat energy by electromagnetic waves in the infrared part of the spectrum and this sort of energy can be transferred through a vacuum. It is important to note that heat or thermal energy is not the same as temperature; heat is measured in joules whereas temperature is usually measured in Kelvin. We all know that some things heat up more easily than others but why is this the case? The reason is due to a property of the substance called the specific heat capacity. It is defined as the energy required to raise the temperature of a unit mass of a substance by one kelvin. The formula which relates the change in the internal energy of a body and the change in temperature of the body is ΔE=mcΔθ. Where delta E is the change in internal energy, m is the mass of the substance being heated, c is the specific heat capacity and delta theta is the change in temperature of the substance which can be in kelvin or Celsius since the change would be the same. You can use this formula to measure the specific heat capacity of a liquid for example with this simple experiment. Pour a known mass of liquid into a calorimeter, which will reduce heat losses to ensure most of the energy put in, is used to heat the liquid. The calorimeter will have a heating element inside it connected to a power supply with an ammeter and voltmeter in the circuit. A thermometer will also be placed in the calorimeter to measure the change in temperature. Finally a stopwatch should be used to measure the time it takes to go from it’s initial temperature to the it’s final temperature. Then using the equation E=IVt and ΔE=mcΔθ we can find the specific heat capacity as c=IVt/mΔθ. When you heat a solid it raises the kinetic energy of the molecules, which as a result raises the internal energy of the substance. However when you continue to heat the substance it will reach a point where all of the energy supplied will go into meting the substance whilst keeping it at a constant temperature. So the potential energy of the particles will increase whilst the kinetic energy remains constant. The energy needed to change the state of a unit mass of a substance from solid to liquid or from liquid to solid at constant temperature is called the specific latent heat of fusion. Whereas the energy required to change the state of a unit mass of a substance from liquid to gas or from gas to liquid at constant temperature is called the specific latent heat of vaporisation. If you were to sketch a graph of temperature against time when heating a substance you can see that when it changes state, there is no change in temperature until it all the substance reaches this state. References: 1. CGP AS & A2 Physics for OCR A, ISBN: 9781847624192
Views: 29611 DoodleScience
Calculating Power and Fuses | GCSE Physics | Doodle Science
 
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Follow me!: https://twitter.com/DoodleSci Doodle Science teaches you high school physics in a less boring way in almost no time! Script: Power is a measure of how quickly energy is transferred and it's measured in Watts. The more energy that is transferred in a certain time, the greater the power. A 100 W light bulb transfers more electrical energy each second than a 60 W light bulb. You can work out power using a simple equation. Power is the amount of energy transferred in joules over the time taken in seconds. For example an electric lamp transfers 500J in 5s. Its power is 100W. You can also calculate the power of an electrical appliance by knowing the current that flows through it and the potential difference across it. You simply multiply the current in Amps by the Potential difference in Volts. For example, in this diagram: what is the power of 5A, 1.5 V electric heater, well that's simply 7.5W. Fuses play an important role in making sure our appliances don't fry when a surge of electricity flows through them. By rearranging the equation P=IV we can work out the best fuse to use. For example what current flows through a 1.15kW electric fire with a voltage of 230V? Well that's 5 amps. Seeing as fuses usually come in the standard ratings of 3A, 5A and 13A, the best option here would be the 13A as the other ones would blow without a surge at all.
Views: 11761 DoodleScience
Heat Transfer - Conduction and Convection | GCSE Physics | Doodle Science
 
01:27
Thanks for Watching! Like and Subscribe if you enjoyed and learnt something! This is the new Channel just for Doodle Science! Script: Conduction is the transfer of heat between substances that are in direct contact with each other and it mainly happens in solids. The heat is conducted from atom to atom using the kinetic energy of the particles, in other words by vibrating. The better the conductor, the more rapidly heat will transfer. Have you ever noticed that metal benches tend to feel colder than a wooden ones? Believe it or not, they are not colder! They only feel colder because they conduct heat away from your bottom better than wood and you perceive the heat that is leaving your bum as cold. Metals are particularly good at conducting heat because of their free electrons that move about the structure colliding with the positive ions and transferring the kinetic energy to them. Convection happens in gases and liquids. As a gas or a liquid is heated, it warms, expands, and rises because it is less dense. When the gas or liquid cools, it becomes denser and falls. As the gas or liquid warms and rises, or cools and falls, it creates a convection current, which is what transfers the heat from one place to another. For example when you turn on your radiator, despite the name the room is heated by convection, as the air is heated above the radiator, it expands, rises and the cooler, denser air sinks causing a convection current around the room.
Views: 98116 DoodleScience
Total Internal Reflection | GCSE Physics | Doodle Science
 
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GCSE Science Doodle Science teaches you high school physics in a less boring way in almost no time! Follow me: https://twitter.com/DoodleSci You can support me at: https://patreon.com/doodlescience Script: Optical fibres can carry information using visible light and something called total internal reflection. It works by bouncing waves off the sides of a thin piece of plastic or glass until it emerges at the end. Total internal reflection can only happen when the light wave is travelling from a denser substance like plastic, to a less dense one like air. Whether total internal reflection will occur depends on whether the angle of incidence is greater than the critical angle. If the angle of incidence is less than the critical angle then most of the light passes out but a little bit is internally reflected. As you increase the angle of incidence, more light gets internally reflected and less light is refracted out. Once the angle of incidence is greater than the critical angle, no light is refracted and all of the light is internally reflected, creating total internal reflection. Different materials have different critical angles and it depends on the refractive index. They are related by this formula: where the refractive index is 1/sin of the critical angle. For example diamond has a refractive index of 2.419. By rearranging the equation we can work out its critical angle of 24.4 degrees. As I mentioned earlier total internal reflection is used in optical fibres, which are very useful for transferring information over long distances very quickly such as your broadband. They are also used as little cameras in keyhole surgery so that the surgeon can see what they are doing without the need to cut a big hole in someone. References: 1. http://www.bbc.co.uk/education/subjects/zrkw2hv 2. CGP GCSE Physics AQA Revision Guide.
Views: 19184 DoodleScience
U-Values and Specific Heat Capacity | GCSE Physics | Doodle Science
 
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Follow me!: https://twitter.com/DoodleSci Doodle Science teaches you high school physics in a less boring way in almost no time! Script: U-values measure how effective a material is an insulator. The lower the U-value, the better the material is as a heat insulator. For example, a cavity wall has a u-value of 1.6, so most of the heat inside the house will stay in the house because the cavity wall will prevent heat loss. Whereas a stone brick wall has a U-value of 2, so the heat will be lost from the house a lot easier and you'll end up paying more on your electricity bills, not to mention freezing your socks off. The specific heat capacity of a substance is the amount of energy needed to change the temperature of 1 kg of the substance by 1°C. Different substances have different specific heat capacities.
Views: 17339 DoodleScience
Ultrasound | GCSE Physics | Doodle Science
 
01:51
Follow me!: https://twitter.com/DoodleSci Doodle Science teaches you high school physics in a less boring way in almost no time! GCSE Science Script: The range of human hearing is 20Hz to 20,000Hz. Ultrasound waves are just sound waves with a frequency above 20,000Hz. When ultrasound reaches a boundary between two media with different densities, some are partially reflected back and the rest pass through. This fact is used in industry to detect cracks or flaws in materials such as metal. They calculate the distance travelled by the ultrasound wave using the simple equation you probably all know, s=vt, where s is the distance in m, v is the speed in m/s and t is the time in seconds. We can work this out by using an oscilloscope trace, take this one for example showing the waves being rebounded from a crack in a piece of aluminium. There are 120 microseconds between the generated pulse and the reflected pulse. 120 microseconds is 120x10^-6 seconds. Now all we need to do is sub this value along with the speed of sound in aluminium into the equation to find the distance of 0.758m. But remember this is double the distance because the time we measured was the time it took the waves to travel to the crack and back. So the actual distance is half this. Because ultrasound partially reflects at the boundary of different media, it is extremely useful for use in pre-natal scanning. It partially reflects at all the different types of tissue, which can be interpreted by a computer to put together an image. Very high frequency ultrasound waves have other medical uses too like breaking up kidney big stones into smaller pieces so that they can be passed out with the urine with minimal pain.
Views: 13240 DoodleScience
Series and Parallel Circuits | GCSE Physics | Doodle Science
 
01:21
Follow me!: https://twitter.com/DoodleSci Doodle Science teaches you high school physics in a less boring way in almost no time! Script: There are two kinds of electrical circuits, series and parallel. Components that are connected one after another on the same loop of the circuit are connected in series. If one lamp were to break in a series circuit, all the lamps would stop working so it's hard to tell where the source of the problem is. Components that are connected on separate loops are connected in parallel. If one lamp breaks, the other lamp will still light which makes it a lot easier to fix. When two or more components are connected in series, the same current flows through each component. But the voltage is shared through the components. This means that if you add together the voltages across each component connected in series, the total equals the voltage of the power supply. In a parallel circuit however, the voltage stays the same throughout the circuit but the current gets divided up through the components. To measure the current of a particular position in a circuit, an ammeter can be placed in series. So in this case A1 will have the same amps flowing through it as A2. In a parallel circuit however A1 will have more amps than A2. To measure the voltage, a voltmeter must be fitted in parallel to the circuit. In this case, V1 will have half the voltage as V2. But in the parallel circuit, V1 and V2 will have exactly the same voltage passing through them.
Views: 23041 DoodleScience
Newton's Laws of Motion | A-Level Physics | Doodle Science
 
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A Level Physics Doodle Science teaches you high school and College physics in a less boring way in almost no time! Follow me: https://twitter.com/DoodleSci You can support me at: https://patreon.com/doodlescience Script: Newton’s first law of motion states that a body will remain at rest or continue to move with constant velocity unless acted on by a resultant force. For example, if you threw a ball in space, it would continue to move with a constant velocity until it collided with something. Newton’s second law states that the resultant force on an object is proportional to the rate of change of momentum and acts in the same direction as the change of momentum. This gives us the formula F = change in momentum/ change in time. For objects of constant mass this formula can be rearranged like so to give the much more familiar F=ma. Momentum is the quantity of motion of a moving body. It is defined as the product of mass x velocity. Since velocity is a vector quantity, meaning it has both magnitude and direction, momentum must be a vector quantity too. For example, a lorry of mass 10000kg is initially travelling at 20m/s. The lorry driver applies the brakes and slows down to 5m/s, which takes 5 seconds. From this we can work out the initial momentum of the lorry to be 200,000kgm/s. The final momentum to be 50,000kgm/s and the average braking force can be calculated using Newton’s second law, which turns out to be -30,000N. The negative sign shows that the force acts in the opposite direction to the direction of motion because it is decelerating the lorry. Newton’s third law states that when one body exerts a force on a second body, the second body exerts a force on the first body, which is equal in magnitude but opposite in direction. This is the reason why your hand hurts when you punch a wall or why there is no skill in a game of conkers. The force one conker exerts on another will experience the same force exerted on it; so the skill lies only in picking the strongest conker. Impulse is the force x the time for which the force acts. Since force is a vector quantity, impulse must also be a vector. By rearranging the formula for newton’s second law you can see that Impulse also equals the change in momentum and is therefore measured in kgm/s or Ns. You can plot a force-time graph to show how the force varies with time; the area under this graph is the impulse of the force. For example, this curve of the force acting on a football being kicked can be approximated to a triangle; this makes it a lot easier to work out the area, which is 10Ns. If the ball had a mass of 0.6kg and was kicked from rest, then since Impulse = change in momentum, you can work out the speed of the ball when it leaves your foot to be 16.7m/s. References: 1. CGP AS & A2 Physics for OCR A, ISBN: 9781847624192
Views: 21649 DoodleScience
The Kinetic Theory | GCSE Physics | Doodle Science
 
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Here's a new Doodle Science video! Please Subscribe and Like if you enjoyed the video and want to see more! This is my new Channel just for Doodle Science videos. Script: 1. The kinetic theory explains the properties of the different states of matter. 2. All the particles in a solid liquid and gas are the same, the only thing that changes, is the amount of energy they have (turbine drawing). 3. Solids have a low amount of energy, too low to overcome the strong bonds that hold the particles together in a regular pattern, but not too low to stop movement all together, as they still vibrate about a fixed position. Solids are also incompressible because there is no free space for the particles to move into. If we give a solid some more energy, it will eventually loosen the bonds between the particles and allow them to move over each other and take the shape of its container, which is what we call a liquid. Similarly, liquids cannot be compressed because there are no free spaces between the particles. Which is why, if you were to jump of a really high diving board, the particles in the water below would for a split second represent the properties of concrete because the particles haven't had time to move out the way for the unfortunate diver. Gases have a lot of energy and move about their container very quickly and unlike solids and liquids, they can be compressed because there is lots of space for the particles to move into. Which is how a paintball gun works, by compressing the air very closely inside a tank and releasing it 4. in a short burst to propel the projectile onto someone's backside. OUCH!
Views: 84218 DoodleScience
Refraction and Diffraction | GCSE Physics | Doodle Science
 
01:25
Follow me!: https://twitter.com/DoodleSci Doodle Science teaches you high school physics in a less boring way in almost no time! Script: Sound waves and light waves change speed when they pass across the boundary between two substances with different densities, such as air and water. This causes them to change direction and this effect is called refraction. If a light ray hits a block of glass at an angle, it's speed and direction changes. Where the light hits, we draw a line perpendicular to the glass block called the normal. From the normal we can measure the angle of incidence and the angle of refraction. The angle of refraction is always less than the angle of incidence. The ray then leaves the glass block parallel to the original ray. When waves meet a gap in a barrier, they carry on through the gap. However, the waves spread out to some extent into the area beyond the gap. This is called diffraction. The extent of the spreading depends on how the width of the gap compares to the wavelength of the waves. For example, when sound travels through a door you can still hear it even though you're not standing in front of the doorway. But when light travels though a doorway, it casts and sharp shadow because the waves have only diffracted a tiny bit. Diffraction allows radio and microwaves to be transmitted behind hills and mountains so people who live there can still get the connection, but having said that I think this guy is kinda screwed.
Views: 35940 DoodleScience
Momentum | GCSE Physics | Doodle Science
 
01:51
Follow me!: https://twitter.com/DoodleSci Doodle Science teaches you high school physics in a less boring way in almost no time! Script: Every moving object has momentum. This is the tendency of the object to keep moving in the same direction unless acted upon by an external force. You'll have a hard time trying to change the direction of movement of an object with a lot of momentum. Unless you're Neo of course. It depends on an object's mass and velocity. So the equation for calculating it is p=mv where p is the momentum in kg m/s; m is the mass in kg and v is the velocity in m/s. A basic example of this would be the momentum of a 20kg trolley travelling at 2m/s would have a momentum of 40kg m/s. However, calculating momentum in a collision isn't as straight forward. To do this we use the conservation of momentum law, which states the amount of momentum before the collision is equal to the momentum after the collision. If a car has a mass of 1000kg and is travelling at 7m/s and hits the back of another car with a mass of 1500kg which was stationary before the collision, then we can work out the velocity of the two cars as they roll off as a single mass. Firstly we work out the momentum of each object individually. So the first car has a momentum of 10500kg m/s and the second car has a momentum of 0kg m/s. Then we add them together, but because velocity has direction, so does momentum and so we have to make one of the values negative to show it's moving in the opposite direction. In this case it doesn't matter because it's zero. Now we know the momentum before the collision we also know it after the collision so all we do now is add the masses of the two cars together and divide it from the momentum to get 4.2m/s.
Views: 30543 DoodleScience
Transformers and the National Grid | GCSE Physics | Doodle Science
 
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Follow me!: https://twitter.com/DoodleSci Doodle Science teaches you high school physics in a less boring way in almost no time! Script: Electricity is transferred from power stations to consumers through the wires and cables of the National Grid. When a current flows through a wire some energy is lost as heat. The higher the current, the more heat is lost. To reduce these losses, the National Grid transmits electricity at a low current and a high voltage. Transformers are used to increase and decrease the voltage of an alternating current. No not those transformers, the boring ones. A transformer that increases the voltage is called a step up transformer and one that decreases the voltage is a step down transformer. Power stations produce electricity at approximately 25,000 Volts. Step up transformers increase the voltage to transmit electricity through the National Grid power lines more efficiently. This reduces energy losses during transmission but the voltages would fry your equipment at home. Step-down transformers are used locally to reduce the voltage to safe levels. In summary, the electricity produced from a power station goes to a step up transformer, the high voltage power cables, a step down transformer and eventually to power the pixels of the screen you're watching this video on.
Views: 16402 DoodleScience
Correcting Vision | GCSE Physics | Doodle Science
 
02:07
GCSE Science Follow me!: https://twitter.com/DoodleSci Doodle Science teaches you high school physics in a less boring way in almost no time! Script: Vision defects generally come in two different ways called short sightedness and long sightedness. A person who has short sight can see near objects clearly, but struggles to focus on distant ones. This is caused by one or two reasons. Firstly the eyeball could be elongated such that the light gets focused in front of the retina which produces a blurry image. Another reason is due to the lens being too powerful, again, resulting in the light converging to a point in front of the retina. The way to correct short sightedness is to place a diverging lens in front of the eye, in the form of glasses of course. This spreads the light out slightly before it reaches the eyes so the light gets focused properly inside it. For someone with long sight, the opposite occurs, they can see distant objects clearly but their near point is further than someone with good vision. The reasons are due to the eyeball being too short which ends up focusing the light behind the retina. Or the lens is too weak to converge the light properly so the focal point is also behind the retina. This is often a result of ageing, which is why you usually need glasses when you get older. The lens used in this case is a converging lens. Obviously different people will have different amounts of vision defects, which is where the power of the lens is important. The power of a lens can be calculated by using the simple equation P=1/f. Where P is the power in diopters and f is the focal length in metres. The power of a diverging lens is always negative since the focal point is in front of the lens so is measured as a negative value. For example a diverging lens with a focal length of -0.15m has a power of -6.67 diopters. If glasses aren’t for you then you can always go for the permanent option of laser eye surgery to fix your vision defect. This works by the laser cutting into the cornea and reshaping it, such that the light focuses directly onto the retina. It apparently doesn’t hurt during the procedure but I can’t imagine it to be the most comfortable thing either! References: 1. http://www.bbc.co.uk/education/subjects/zrkw2hv 2. CGP GCSE Physics AQA Revision Guide.
Views: 15395 DoodleScience
Diodes, LEDs, Thermistors and LDRs | GCSE Physics | Doodle Science
 
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Follow me!: https://twitter.com/DoodleSci Doodle Science teaches you high school physics in a less boring way in almost no time! Script: Diodes are electronic components, which can be used to regulate the potential difference in circuits and to make logic gates. Diodes have a very high resistance in one direction, (ideally infinite) and a very low resistance in the other direction (ideally zero). If you were to measure the voltage across a diode and the current passing through it and plot it on a graph it would look something like this. As you can see, when you flip the diode the other way, there is a very high resistance. A light-emitting diode, LED, produces light when a current flows through it in the forward direction. Because they use so little energy and last a substantial time longer than conventional filament bulbs, they are becoming more popular. Thermistors are used as temperature sensors, for example in fire alarms. They are made from semiconducting materials that lower resistance as they increase in temperature. So when things get hot, the current passes through them and the alarm is triggered. Besides they're cool because the symbol looks like it's playing hockey (joke courtesy of Samuel Ashcroft). Light dependant resistors or LDRs are used to detect light levels. Their resistance decreases as the light intensity increases. So when it's bright, the current flows through it more easily. But the symbol isn't nearly as interesting.
Views: 12465 DoodleScience
Renewable Energy Resources: Part 2 | GCSE Physics | Doodle Science
 
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Follow me!: https://twitter.com/DoodleSci Doodle Science teaches you high school physics in a less boring way in almost no time! Script: Geothermal energy uses hot water and steam from deep underground to drive turbines. Radioactive decay of substances like uranium heats up rocks, which may heat water that rises as steam. In some places there may be hot rocks but no water. In this situation, deep wells can be drilled down to the hot rocks and cold water pumped down. The water runs through the rocks where it's heated up and returns to the surface as hot water and steam, where its energy can be used to drive turbines and electricity generators. The advantages are that there are no pollutant gases produced. However, most parts of the world do not have suitable areas where geothermal energy can be exploited. Finally, you can use solar cells to generate electricity. They convert light energy directly into electrical energy. The advantages are that they can be used in remote areas because they create electricity directly. However, solar cells are expensive and inefficient, so the cost of their electricity is high. But the cost is going down year by year and eventually, everyone will want it.
Views: 50426 DoodleScience
Evaporation and Condensation | GCSE Physics | Doodle Science
 
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Follow me on twitter: https://twitter.com/DoodleSci to get all the latest info! This video explains everything you need to know about Evaporation and Condensation in a less boring way;) Script: Evaporation involves a liquid changing into a gas. The particles in a liquid have different energies, some will have enough energy to escape from the liquid and become a gas whilst the remaining particles in the liquid have a lower average kinetic energy so will stay there and the liquid will cool down as evaporation happens. This is why sweating cools you down, by leaving behind the cooler liquid on your skin. The sweat absorbs energy from your skin so that it can continue to evaporate and cool you down even more. The rate of evaporation increases if the temperature of the liquid is increased, if the surface area of the liquid is larger or the air moving over the surface is more violent. Condensation involves a gas turning into a liquid. The particles in a gas have different energies. Some may not have enough energy to remain as separate particles, particularly if the gas is cooled down. this causes them to come close together and bonds form between them. Energy is released when this happens. This is why steam touching your skin can cause scalds: not only is the steam hot, but energy is released into your skin as the steam condenses which only adds to the pain.
Views: 42934 DoodleScience
Energy Transfer and Efficiency | GCSE Physics | Doodle Science
 
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Follow me!: https://twitter.com/DoodleSci Doodle Science teaches you high school physics in a less boring way in almost no time! Script: Different types of energy can be transferred from one type to another. You can see that a car engine transfers chemical energy, which is stored in the fuel, into kinetic energy in the engine and wheels so it can get you from A to B. In a lamp the electrical input is converted into light energy. However not all the energy put in is turned into useful energy, some of it is turned into energy we don't need such as heat. Sankey diagrams summarise all the energy transfers taking place in a process. The thicker the arrow, the greater the amount of energy involved. This Sankey diagram for an electric lamp shows that most of the electrical energy is transferred as heat rather than light. This means it's very inefficient. We can calculate efficiency using this simple formula, useful energy, in this case 10J divided by the total energy input, which is 100J, which gives us an efficiency of 0.1 or 10% if you times it by 100.
Views: 63180 DoodleScience
The Big Bang Theory and Red-Shift | GCSE Physics | Doodle Science
 
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Follow me!: https://twitter.com/DoodleSci Doodle Science teaches you high school physics in a less boring way in almost no time! Script: The big bang theory is currently the accepted theory for how the universe was created. The theory states that originally all the matter in the universe was concentrated into a single incredibly tiny point, which exploded and began to enlarge rapidly and is still expanding today. We know the universe is expanding because of the Doppler effect. You may have noticed that when an ambulance or police car goes past, its siren is high-pitched as it comes towards you, then becomes low-pitched as it goes away. This effect, where there is a change in frequency and wavelength, is called the Doppler effect and it doesn't only happen with sound. We can see it happening with light when we look at distant stars. The light is being stretched towards the red end of the spectrum because the object is moving away from us, just as it was with the police car. Evidence for this is shown by the location of these black lines in the spectrum of our Sun and in other stars. The black lines are where different elements such as helium absorb light. They are shifted towards the red end of the spectrum because of the Doppler effect. But be careful, just because things moving away from us are shifted towards the red end of the spectrum, doesn't mean they necessarily look red, they just have a longer wavelength.
Views: 26743 DoodleScience
Work Done and Power | GCSE Physics | Doodle Science
 
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Follow me!: https://twitter.com/DoodleSci Doodle Science teaches you high school physics in a less boring way in almost no time! Script: Work is the amount of energy transferred when a force moves something. For example when you carry something upstairs or a lift a heavy object, work is being done. You can calculate the amount of work being done by knowing the force applied and the distance the object has travelled. The work is measured in Joules; the force in Newton's and the distance in meters. If this guy pushes this box with a force of 300N and he moves it by 2m, the work done is 600J. Lets just say it took him 20 seconds to do it, but there is another guy who pushed a box in 10 seconds with the same force and by the same distance. It's tempting to say that the second guy did more work, but the time is irrelevant when it comes to the work done. So cheer up, you can both have medals. The difference is the power at which they pushed the box. You can calculate the power in Watts by dividing the work done, by the time in seconds. In this case the first guy pushed the box with a power of 30 Watts and the other guy pushed it with a power of 60 Watts, who do you think's stronger?
Views: 37217 DoodleScience
Renewable Energy Resources: Part 1 | GCSE Physics | Doodle Science
 
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Follow me!: https://twitter.com/DoodleSci Doodle Science teaches you high school physics in a less boring way in almost no time! Script: Renewable energy resources are being developed because we are running out of fossil fuels at an exponential rate. The wind is produced as a result of giant convection currents in the Earth's atmosphere, which are driven by heat energy from the sun. Wind turbines use the wind to drive turbines directly. The blades are connected to a housing, which contains gears linked to a generator. As the wind blows, it transfers some of its kinetic energy to the blades, which turn and drive the generator. The advantages are that there are no fuel costs and no harmful pollutant gases are produced. However, they depend on wind, if there is no wind, there's no electricity. Like the wind, water can be used to drive turbines directly. Wave machines use the kinetic energy in this movement to drive electricity generators. Another way of using the water is to build a tidal barrage over a river estuary to make use of the kinetic energy in the moving water. The barrage contains electricity generators, which are driven by the water rushing through tubes in the barrage. Hydroelectric power stations are dams built across a river valley. The water high up behind the dam contains gravitational potential energy. This is transferred to kinetic energy as the water rushes down through tubes inside the dam. The moving water drives electrical generators, which may be built inside the dam. Water produced energy is good because no harmful polluting gases are produced and tidal barrages and hydroelectric power stations are very reliable and can be easily switched on. However, tidal barrages destroy the habitat of estuary species and hydroelectricity dams flood farmland and push people from their homes.
Views: 104335 DoodleScience
Collisions | A-Level Physics | Doodle Science
 
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A Level Physics Doodle Science teaches you high school and College physics in a less boring way in almost no time! Follow me: https://twitter.com/DoodleSci You can support me at: https://patreon.com/doodlescience Script: The idea of conservation of momentum can be used to work out what will happen when things collide. Conservation of momentum states that the total momentum of a closed system is constant. This means that the total momentum before a collision is equal to the total momentum after the collision. For example, an ice hockey player of mass 85kg, charges into a practice dummy of mass 250kg, with a velocity of 10m/s. Since the dummy is covered in glue, the hockey player and the dummy both move off together. Using the fact that momentum before = momentum after we can calculate the velocity of the combination to be 2.54m/s. There are two types of collision, elastic and inelastic. An elastic collision is a collision with no loss of kinetic energy. This only occurs on a microscopic level, where heat cannot be generated, such as the collision between two gas molecules. An inelastic collision is a collision with some loss of kinetic energy, this is usually the case with most collisions because the kinetic energy is transferred into other forms such has heat and sound. For example, a particle of mass 5kg is moving at 4m/s when it strikes a second particle of mass 10kg moving at 2m/s towards the first particle. After the collision, the first particle has a velocity of 2.80m/s in the opposite direction to which it was first travelling. Using conservation of momentum here we can work out the velocity of the second particle to be 1.40m/s. Before the collision, the kinetic energy was 60J. After the collision the kinetic energy was only 29.4J. This means there was a loss of 30.6J of kinetic energy, so the collision was inelastic. References: 1. CGP AS & A2 Physics for OCR A, ISBN: 9781847624192
Views: 6331 DoodleScience
Refraction and Refractive Index | GCSE Physics | Doodle Science
 
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Follow me!: https://twitter.com/DoodleSci Doodle Science teaches you high school physics in a less boring way in almost no time! GCSE Science Script: Refraction happens when light changes direction when it travels between substances of different densities. The difference in densities between substances affects the amount of refraction that takes place. Light slows down when passing into a denser substance, like from air to glass. The angle of refraction is smaller than the angle of incidence as the light bends toward the normal. Passing through a less dense substance means the light speeds up and the rays bend away from the normal. I use the acronym FAST to remember which ones which so I don’t get confused when drawing it. Every transparent substance has a refractive index, which is the amount that it slows the light down compared to the speed of light in a vacuum. It’s calculated using the equation sin i / sin r. Where “i” is the angle of incidence and r is the angle of refraction. Take this example, where the angle of incidence is 65 degrees and the angle of refraction is 40 degrees. This gives us a refractive index of 1.41 and will bend the light towards the normal. Refractive indices are good when it comes to making lenses, so you can have powerful lenses without looking like this…
Views: 14215 DoodleScience
The Energy Types | GCSE Physics | Doodle Science
 
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Follow me!: https://twitter.com/DoodleSci Doodle Science teaches you high school physics in a less boring way in almost no time! Script: There are 10 types of energy. Magnetic, the energy in magnets, electromagnets and the Earth's magnetic field. Kinetic, the energy in moving objects, like this bullet out of a gun. Heat, which is also called thermal energy. Light, the energy from the sun and your phone. Gravitational potential, the energy stores in raised objects like a skydivers jumping from 15,000 feet. Chemical, the energy stored in cheese, fuel and batteries. Sound, the energy released by vibrating objects such as my voice that you're listening to now (hopefully). Electrical, the energy in lightning and the energy that powers your toaster. Elastic potential, the energy stored in stretched or squashed objects like a catapult to the bum. And finally, Nuclear, the coolest of them all, stored in the nuclei of atoms. Now that's a lot to take in, but remember, Not Every Clever Get Might Know Spiders Have Eight Legs and you'll be fine.
Views: 26800 DoodleScience
X-Rays | GCSE Physics | Doodle Science
 
01:19
Follow me!: https://twitter.com/DoodleSci Doodle Science teaches you high school physics in a less boring way in almost no time! GCSE Science Script: X-Rays are part of the electromagnetic spectrum and have a wavelength of about the diameter of an atom. Because of this small wavelength they are able to penetrate healthy tissue but are absorbed by denser material like bone and metal. They also affect photographic film or CCDs in digital cameras in the same way as light, which is why they are used to diagnose bone fractures and dental problems. The x-rays pass through the healthy tissue, turning the image black and the light regions are where the x-rays were absorbed, like your bones or a nasty big tumor. CT scans or CAT scans also use X rays but they take images from multiple directions building up a 3D image of the patient inside. This gives the doctor a much more detailed view of the problem. X-Rays are known as ionising radiation, which means they can damage the DNA in cells causing mutations and potentially cancer. High doses of x-rays however can be used to kill cancerous cells and is used in radiotherapy. So I’m sure you’d agree finding the right amount of exposure is crucial. This is especially important to radiographers as they could be exposed to lethal doses of x-rays over the years. They always stand behind lead screens or even leave the room when you’re being scanned to reduce the risks to them. Don’t let me scare you next time you go for an x-ray though, you get exposed to more radiation on a flight from London to New York from the background radiation left over from the big bang!
Views: 11432 DoodleScience
Atomic Structure | GCSE Physics | Doodle Science
 
01:56
Follow me!: https://twitter.com/DoodleSci Doodle Science teaches you high school physics in a less boring way in almost no time!
Views: 9045 DoodleScience
Newton's Second Law of Motion (F=ma) | GCSE Physics | Doodle Science
 
01:15
Follow me!: https://twitter.com/DoodleSci Doodle Science teaches you high school physics in a less boring way in almost no time! Script: An object will accelerate in the direction of the resultant force. The bigger the force, the greater the acceleration. By doubling the size of the force, it doubles the acceleration. Also, a force acting on a large mass will accelerate it less than the same force acting on a smaller mass. Doubling the mass of an object halves it's acceleration. The relationship between these variables can be shown by the equation, F=ma. Where F is the resultant force in Newtons. M is the mass in Kg and A is the acceleration of the object in meters per second squared. For example, If a car has a mass of 700kg and the driver pushes the car with an acceleration of 0.05m/s^2 then the force applied was 35N. You can also use the formula to work out the acceleration and the mass. And to leave you with a cool fact, a newton is approximately the weight of an apple.
Views: 94302 DoodleScience
Non-Renewable Energy Resources | GCSE Physics | Doodle Science
 
01:23
Follow me!: https://twitter.com/DoodleSci Doodle Science teaches you high school physics in a less boring way in almost no time! Script: Fossil fuels are non-renewable energy resources; these are coal, oil and natural gas. They were formed from the remains of living organisms millions of years ago and they release heat energy when they are burned. This heat is used to turn water into steam, which is used to turn a turbine, which then drives a generator to generate electricity. There are downsides however, fossil fuels release sulphur dioxide and carbon dioxide which lead to acid rain and an increase in global warming. Another form of non-renewable energy is Nuclear. The main nuclear fuels are uranium and plutonium. The nuclei of these large atoms are split in a process called nuclear fission to release a great deal of heat. The heat energy is again used to boil water. The kinetic energy in the expanding steam spins turbines, which then drive generators to produce electricity. Unlike fossil fuels, nuclear fuels do not produce carbon or sulphur dioxide. However, they do have the risk of a fault where large amounts of radioactive material could be released into the environment such as the disaster of Chernobyl in 1986.
Views: 128714 DoodleScience
Half-Life | GCSE Physics | Doodle Science
 
01:42
Follow me!: https://twitter.com/DoodleSci Doodle Science teaches you high school physics in a less boring way in almost no time! GCSE Science Script: When a radioactive atom goes through alpha or beta decay, the atom itself changes into a different element. For example, carbon-14 decays to nitrogen-14 when it emits beta radiation. It’s impossible to predict when an individual atom might decay because it’s completely random. What you can do is measure the time it takes for half the atoms in a radioactive substance to decay. We call this a half-life. We can use graphs to find out the half-life of a radioactive substance. All we have to do is measure the count rate over time and plot the decay curve. As you can see the count rate drops from 100 to 50 in 2 days, from 50 to 25 in another 2 days, to 12.5 and so on. Alpha and beta decay can be represented through nuclear equations. An alpha particle consists of two protons and two neutrons, this means that the mass number on an atom would decrease by 4 and the atomic number by 2. For example, radon-219 would decay into polonium-215 and emit an alpha particle in the process. This is represented in an equation like this. In beta decay, a neutron changes into a proton and a high-energy electron is released. The nucleus now has one less neutron but one more proton, so the mass number stays the same but the atomic number increases by 1. For example, thorium-234 decays into protactinium-234 and a beta particle is released. As you can see the beta particle has a -1 as its atomic number to represent the additional proton that was added. Seems a little counter intuitive but that’s just the way it is.
Views: 23913 DoodleScience

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