Gravitational Potential Energy (GCSE Physics)

Gravitational Potential Energy

Gravitational Potential Energy, GPE

Gravity is a force that attracts objects towards the centre of the Earth. In order to overcome the force of gravity and lift an object up, we have to do work, which requires energy.

As an object is lifted into the air, it gains gravitational potential energy (GPE). This energy has been transferred from kinetic or chemical energy. The gain in GPE is equivalent to the amount of work done when lifting the object up.

Just like kinetic energy, the mass is important too. GPE is determined by mass and height.

Calculating GPE

We can calculate the amount of gravitational potential energy an object has gained using the following formula.

Where:

• gravitational potential energy, Ep, in joules, J
• mass, m, in kilograms, kg
• gravitational field strength, g, in newtons per kilogram, N/kg
• height, h, in metres, m

Question: Joe weighs 70 kg. He climbs up a tree 12m tall. Calculate his GPE in kJ, giving your answer to 1 decimal place. Take the value of g as 9.8 N/kg.

1. Write out the formula.
   Firstly, we need to write out the correct formula for gravitational potential energy.

GPE = 8232 Joules
GPE = 8.2 kJ

Question: A diver weighing 72kg jumps from a height of 20 metres to ground level. What is the loss in gravitational potential energy he experiences? (Assume the gravitational field strength g is 10 N / kg, and that the effects of friction and air resistance are negligible).

Change in GPE = Mass x 10 x Distance Raised
Change in GPE = 72 x 10 x -20 = – 14400 J
Loss of 14400J GPE