Energy, work and power

energy

ability to do work

kinetic

energy due to motion - all moving objects have kinetic energy - cars, runners

potential

energy an object stored due to having changed position, shape or state

gravitational potential

energy gained when an object is lifted - planes, divers

chemical potential

energy stored in fuel - food, batteries

elastic (strain) potential

stretched rubber band or spring can do work when it is released - catapults, stretched elastic. bands

nuclear

energy stored in the nucleus - nucleus power stations, the sun

electrostatic energy

energy stored when charges are separated or squashed together - thunderclouds

internal (thermal) energy

the energy of an object; the total kinetic and potential energies of its particles - hot water, human bodies

what are energy stores

potential energy. This is energy that is not being used but is available

what is energy able to do?

energy can be stored or it can be transferred in an event or process

event

something that happens or takes place, often at a specific time or place

process

a series of actions or steps, often taking place over a long period of time

principle of conservation of energy

energy cannot be created or destroyed; it can only be stored or transferred

formula for kinetic energy

E_k = ½ mv²

E_k = ½ x mass x velocity²

measured in Joules

formula for gravitational potential energy

mass x gravitational acceleration x change in height

(kg) x (m/s²) x (m)

mgΔh

work done

product of force and distance moved in the direction of the force. it is a measure of how much energy is transferred when an object is moved against a resistive force

work done =

energy transferred = change in energy

formula for work done

force x distance moved (in direction of the force)

(N) x (m)

Fd = ΔE

efficiency

the fraction (or percentage) of energy supplied that is usefully transferred

formula for efficiency

(useful energy output / total energy output) x 100%

(useful power output / total power output) x 100%

renewable energy

can be easily replaced in a human lifetime

non-renewable energy

cannot be replaced in a human lifetime

types of renewable energy

• solar

• hydroelectric

• wind

• wave

• tidal

• geothermal

• biomass

types of non renewable energy

• fossil fuels (oil, coal, gas)

• nuclear

which energies do NOT get their energy from the sun

geothermal, nuclear, tidal

energy can be obtained through:

• fossil fuels

• biofuels

• water - waves, tides, hydroelectric dams

• geothermal resources

• nuclear fission

• light from the sun (solar cells)

• infrared and other electromagnetic waves from the sun to heat water

  • wind

nuclear fusion is in

the sun

nuclear fission is in

nuclear reactors

formula for power (watts)

work done / time =
(J) / (s) =

energy transferred / time
(J) / (s)

power

work done per unit time or energy transferred per unit time