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Gravitational Potential Energy (Cambridge O Level Physics)
Revision Note
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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