Movement means energy in an object's kinetic energy store
Energy is trasnferred to the kinetic energy store when an object speeds up and is transferred away from this store when an object slows down
The energy in the kinetic energy store depends on the object's mass and speed
The greater an object's mass and the faster it is going, the more energy there will be in its kinetic store
Kinetic energy(J) = 1/2 x mass(kg) x speed^2((m/s)^2)
Ek(J) = 1/2m(kg)^2((m/s)^2)
A car of mass 2500kg is travelling at 20 m/s. Calculate the energy in its kinetic energy store. Ek = 1/2 x 2500 x 20^2 = 500 000J
Raised objects store energy in gravitational potential energy stores
Lifting an object in a gravitational field requires work. This causes a transfer of energy to the gravitational potential energy (g.p.e.) storeof the raised object
The higher the object is lifted, the more energy is transferred to the gravitational potential energy store
The amount of energy in a g.p.e. store depends on the object's mass, its height and the strength of the gravitational field of the object is in
g.p.e(J) = mass(kg) x gravitational field strength(N/kg) x height(m)
Ep(J) = m(kg)g(N/kg)h(m)
When something falls, energy from its gravitational potential energy store is transferred to its kinetic energy store
For a falling object when there's no air resistance: Energy lost from g.p.e. store = Energy gained in the kinetic energy store
In real life, air resistance acts against all falling objects - it causes some energy to be transferred to other energy stores e.g thermal energy stores of the object and surroundings
Stretching can transfer energy to elastic potential energy stores
So long as the limit of proportionality has not been exceeded, energy in the elasticpotential energy store of a stretched spring can be found using the elastic potential energy formula
Elastic potential energy(J) = 1/2 x spring constant(N/m) x extension^2(m)