Gravitational Potential Energy (Edexcel IGCSE Physics)
Revision Note
Author
LeanderExpertise
Physics
Gravitational Potential Energy
- Energy in the gravitational potential store of an object is defined as:
The energy an object has due to its height in a gravitational field
- This means:
- If an object is lifted up, energy will be transferred to its gravitational store
- If an object falls, energy will be transferred away from its gravitational store
- The gravitational potential energy of an object can be calculated using the equation:
GPE = m × g × h
- Where:
- GPE = 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)
Energy is transferred to the mass's gravitational store as it is lifted above the ground
Gravitational Field Strength
- The gravitational field strength (g) on the Earth is approximately 10 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
Some values for g on the different objects in the Solar System
- The two graphs below show how GPE changes with height for a ball being thrown up in the air and when falling down
Graphs showing the linear relationship between GPE and height
Worked example
A man of mass 70 kg climbs a flight of stairs that is 3 m higher than the floor.
Gravitational field strength is approximately 10 N/kg.
Calculate the increase in energy transferred to his gravitational potential store.
Step 1: List the known quantities
-
- Mass of the man, m = 70 kg
- Gravitational field strength, g = 10 N/kg
- Height, h = 3 m
Step 2: Write down the equation for gravitational potential energy
Step 3: Calculate the gravitational potential energy
Exam Tip
When doing calculations involving gravitational field strength, g, don't panic, you will always be told the value of g in your equation sheet in your exam paper!
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