Gravitational Potential Energy

When an object is above the Earth’s surface, energy is stored in the gravitational potential energy store. This is due to the force of gravity. The amount of gravitational potential energy depends on three things:

1. Mass

2. Gravitational field strength

3. Height above the ground

The higher the object is above the ground, the more energy is transferred to this store. When looking at gravitational potential energy, it is good to explore mass and gravitational field strength.


Mass is a measure of the amount of matter in an object. This means the more matter an object contains, the greater its mass is.

Mass is measured in kilograms (kg)

For example, a 50 kg object has a greater mass than a 10 kg object. An object’s mass stays the same no matter where it is. This means that a 50 kg object will be 50 kg on Earth and 50 kg in space.

Gravitational Field Strength

Gravity is a force that attracts objects to each other. It keeps the Moon orbiting around the Earth and it keeps the Earth in orbit around the Sun.

We are pulled down to the ground because of gravitational forces. These forces pull us in the direction of the centre of the Earth.

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Gravitational field strength is the force per unit of mass, which is measured in newtons per kilogram (N/kg).

The symbol g is used to represent gravitational field strength.

Gravitational field strength is different on the Moon and space when compared to Earth.

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  • Earth’s gravitational field strength is 10 N/kg
  • The Moon’s gravitational field strength is 1.6N/kg
  • The gravitational field strength in space is 0 N/kg

Calculating Gravitational Potential Energy

Below is the equation to work out the gravitational potential energy.

Gravitational potential energy = Mass × Gravitational field strength × Height

  • Ep = 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)

When objects fall, energy is also transferred from gravitational potential energy to kinetic energy (movement energy).