Gravitational Potential Energy (Cambridge (CIE) O Level Physics): Revision Note
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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:
ΔEP = mgΔh
Where:
ΔEP = 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
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
ΔEP = mgΔh
Step 3: Calculate the gravitational potential energy
ΔEP = 70 × 9.8 × 3
ΔEP = 2058 J
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