Gravitational Potential Energy (Oxford AQA IGCSE Combined Science Double Award)
Revision Note
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, Ep, can be calculated using the equation:
Ep = m × g × h
Where:
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)
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
Worked Example
A man of mass 70 kg climbs a flight of stairs 3 m higher than the floor. Gravitational field strength is approximately 9.8 N/kg.
Calculate the energy transferred to the man's gravitational potential energy store.
Answer:
Step 1: List the known quantities
Mass of the man, m = 70 kg
Gravitational field strength, g = 9.8 N/kg
Height, Δh = 3 m
Step 2: Write down the equation for gravitational potential energy
ΔEP = mgΔh
Step 3: Calculate the gravitational potential energy
ΔEP = 70 × 9.8 × 3
ΔEP = 2058 J
Examiner Tip
You do not need to know the gravitational field strength values, even for Earth. You will be given the values if required in the exam.
Last updated:
You've read 0 of your 10 free revision notes
Unlock more, it's free!
Did this page help you?