Gravitational Potential Energy (Oxford AQA IGCSE Combined Science Double Award)

Gravitational Potential Energy

• An object gains energy in its gravitational potential store when it is raised vertically through a gravitational field

• Work is done against the weight of the object, therefore energy is transferred

• This means:

  • If an object is lifted, energy is transferred to its gravitational potential store 

  • If an object falls, energy will be transferred away from its gravitational potential store

Calculating gravitational potential energy

• The amount of energy in an object's gravitational potential store, E_p, can be calculated using the equation:

E_p = m × g × h

• Where:

  • E_p = gravitational potential energy, in joules (J)

  • m = mass, in kilograms (kg)

  • g = gravitational field strength in newtons per kilogram (N/kg)

  • h = height in metres (m)

Gravitational potential energy of a mass lifted through a height

Gravitational field strength

• The gravitational field strength (g) on the Earth is approximately 9.8 N/kg

• The gravitational field strength on the surface of the Moon is less than on the Earth

  • This means it would be easier to lift a mass on the Moon than on the Earth

• The gravitational field strength on the surface of the gas giants (eg. Jupiter and Saturn) is more than on the Earth

  • This means it would be harder to lift a mass on the gas giants than on the Earth

Gravitational field strength on different bodies of the solar system

• Remember that mass is not dependent upon gravitational field strength but weight is