This GCSE Physics quiz on forces will challenge you on the kinetic energy of objects. All objects in motion have kinetic energy. The amount of kinetic energy depends on the speed they are moving and their mass and is measured in joules. When you compare two or more objects moving at the same speed, the heaviest will be the one that has the greater kinetic energy. Objects with more kinetic energy can do more work, which is why high speed collisions or collisions involving larger vehicles are more destructive.
When an object speeds up or slows down, its kinetic energy increases or decreases. When energy is transferred, it means that work has been done - the forces which cause a change in speed therefore do so by doing work. If friction and air resistance are ignored, the kinetic energy changes by an amount that is equal to the work done by the applied force.
Friction and air resistance reduce the amount of kinetic energy by transferring it into heat energy. The law of conservation of energy means that the work done is therefore equal to amount of heat transferred plus the kinetic energy of the object. Kinetic energy can be stored by using a heavy wheel called a flywheel. This spins at high speed on low-friction bearings but most of the time, kinetic energy is transferred from other forms of energy only when it is needed.
For the GCSE, you should be able to discuss the transfer of kinetic energy in particular situations. Examples might include the space shuttle re-entry or meteorites burning up in the atmosphere. It could also include braking systems as they are designed to transfer kinetic energy into heat energy to slow or stop a vehicle. Most vehicles currently use non-renewable fossil fuels as the source of energy that is transferred into kinetic energy.
As humans are becoming more aware of the damage caused to the Earth by large scale burning of fossil fuels, car manufacturers are designing electric cars. There are even cars that produce their electricity from solar cells, some is used to charge the batteries and the rest is transferred directly into kinetic energy without first being stored. These do not emit (give out) gases into the atmosphere but the electrical energy needs to come from somewhere. Most electricity is generated from the burning of fossil fuels so they do cause pollution at the power station. The parts all need to be manufactured, which uses up the Earth's resources and creates more pollution at the factories - there is no such thing as an environmentally-friendly vehicle.
You may also be required to make calculations of kinetic energy or required to work out factors such as speed and mass from knowing the kinetic energy of an object, so make sure that you learn the equation used to work out kinetic energy. The equation includes the term v2 so when the speed of an object is doubled, the kinetic energy increases fourfold.
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