Forces and Energy

work done = energy transferred

W = Fd

W = work done or energy transferred (J)

F = force applied (N)

d = distance moved (m)

ENERGY CAN CHANGE FORM, BUT IS NEVER DESTROYED OR USED UP

For example: when a car crashes it loses kinetic energy. The car no longer has the kinetic energy it had before the crash. Some kinetic energy has become sound and heat. 

Friction between moving objects produces heating - this is because work done to overcome the friction is transeferred as energy that heats the objects that rub together and the surroundings

For example: when a car slows down using its brakes, friction between the brake pads and discs leads to the kinetic energy of the car being transferred to the pads and discs, which get hot.

Ep = mgh

Ep = potential energy (J)

m = mass (kg)

g = gravitational field strength (N/kg)

h = change in height (m)

Gravitational potential energy is the energy stored in an object because of its position in the Earth's gravitational field. The gravitational potential energy of an object increases when it moves up and decreases when the object moves down. 

Ek = 1/2mv²

Ek = kinetic energy (J)

m = mass (kg)

v = speed (m/s)

All moving objects have kinetic energy. The greater the mass and the faster the speed of an object, the more kinetic energy it has.

Power is the rate at which energy is transferred

Power = energy transferred/time taken 

We measure power in watts (W) or kilowatts (kW) or megawatts (mW). One watt is a rate of transfer of energy of 1 joule per second (J/s)