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Gravitational potential energy
Beginner
Energy due to height in a uniform field.
U = mghNear Earth U = mgh relative to a chosen level. The work done by gravity is −ΔU independent of path.
Lifting a 5 kg box 2 m: ΔU = 98 J.
This formula is only valid when g is nearly constant.
In more detail
Gravitational potential energy near Earth's surface is mgh, where h is height above a chosen reference level. It decreases as an object falls and increases as it rises.
Real-world uses
- Hydroelectric dams convert gravitational potential energy of water into electricity.
- Lifts and cranes store potential energy when they raise loads.
- A hydroelectric dam uses the gravitational potential energy of water held at height to drive turbines.
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Frequently asked questions
Why do we use mgh?
It is an approximation valid near Earth's surface where g is roughly constant.
Does potential energy depend on the path?
No. For gravity, it depends only on the height difference.
Does the path taken change the gravitational potential energy?
No. It depends only on the height difference, so the same change occurs however the object moves between the two heights.
Related topics in Work, Energy & Power
Kinetic energy · Work–energy theorem · Potential energy · Elastic potential energy · Conservative forces · Non-conservative forces