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ANYTHING WHICH IS MOVING HAS KINETIC ENERGY. THE GREATER THE MASS AND SPEED,
THE GREATER THE KINETIC ENERGY.
KINETIC ENERGY = ½ X MASS X VELOCITY2
For example: A car has a mass of 2450kg and is travelling at
38m/s. Calculate its kinetic energy.
Answer: 0.5 x 2450 x 382 = 1768900J.
To stop a car the kinetic energy has to be converted to heat energy at the brakes and
tyres: If you double the speed, you double the velocity. But because the velocity is
squared the KE will increase by a factor of four. So you need 4 times the distance to stop.
i. The greater the mass and speed, the greater the KE
ii. KE = ½ x m x v2
iii. When braking, KE has to be converted into heat energy
iv. When you double your speed you quadruple your stopping distance.
ELASTIC POTENTIAL ENERGY: THIS IS STORED WHEN WORK IS DONE ON AN OBJECT TO
CHANGE THE SHAPE.
E.g. springs store potential energy whenever they're compressed or stretched.
GRAVITATIONAL POTENTIAL ENERGY: THE ENERGY STORED IN AN OBJECT WHEN IT IS AT
A HEIGHT AGAINST GRAVITY.
GPE= MASS X GRAVITY X CHANGE IN HEIGHT
You have to move something to increase the GPE and that
energy is released when the object falls.