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:

ΔE_P = mgΔh

Where:
- ΔE_P = change in gravitational potential energy, in joules (J)
- m = mass, in kilograms (kg)
- g = gravitational field strength in newtons per kilogram (N/kg)
- Δh = change in height in metres (m)

Energy in the Gravitational Potential Store

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Energy is transferred to the mass's gravitational store as it is lifted above the ground

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 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

ΔE_P = mgΔh

Step 3: Calculate the gravitational potential energy

ΔE_P = 70 × 9.8 × 3

ΔE_P = 2058 J

Gravitational Potential Energy (Cambridge O Level Physics)

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