Conservation and dissipation of energy

Chemical energy stores

These types of stores include fuels, foods and batteries

Kinetic energy stores

The energy an object has because it is moving

Gravitational potential energy store

The energy stored in an object because of its position, for example above the ground

Elastic potential energy store

The energy stored in a springy object when you stretch or squash it

Thermal energy stores

The energy a substance has because of its temperature

By heating, by waves, by electric current or by a force when it moves an object

How can energy be transferred?

The energy is transferred to the thermal store of its surroundings and sound waves are produced

What happens to the kinetic energy of an object when it hits the ground?

GPE to KE to thermal energy

Describe the energy transfers that happen when a heavy object falls from a height

work done (J) = force (N) x distance (m)

What is the equation for work done?

Change in object's GPE (J) = weight (N) x change of height (m)

How do you calculate the change in an objects GPE?

9.8 N/kg

What is the gravitational field strength on Earth?

Change of GPE (J) = mass (kg) x gravitational field strength (N/kg) x change of height (m)

How do you calculate the change of the gravitational energy store?

Kinetic energy (J) = 1/2 x mass (kg) x speed^2 (v^2)

How do you calculate an object's kinetic energy?

Elastic potential energy (J) = 1/2 x spring constant (N/m) x extension^2 (m^2)

How do you calculate an object's Elastic potential energy?

Useful energy

energy transferred to where it is wanted in the way that is wanted

Wasted energy

Energy that is not usefully transferred

Dissapation

When wasted energy is transferred to the thermal store of the surroundings

The input energy

energy supplied to a device

Efficiency = useful power output/total power input x 100

What is the equation for efficiency?

power (W) = energy transferred (J) / time (s)

What is the equation for power?

Power wasted = total power - useful power output

How do you calculate power wasted?