Part 03 · Work, energy and momentum · Card 4 of 9
Gravitational potential energy
Stored energy due to height, PE = mgh. It can turn into motion when the object falls.
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Analogy
A boulder on a cliff holds energy ready to use.
Example
Lifting a mass
PE = m g hPE = 2 x 9.8 x 5PE = 98 J
In practice
Lifting 2 kg by 5 m stores 98 J.
Practice
Flashcards
- What is gravitational potential energy near Earth?PE = m g h.
Questions people ask
Where do I put the zero of potential energy?
Anywhere you like. Only changes in potential energy matter physically. Pick a convenient level, such as the ground or the lowest point, and measure heights from there. The final answers for speed or work will be the same whichever zero you choose.
Does the path matter for potential energy?
No. Gravity is a conservative force, so the energy change depends only on the start and end heights. Climbing a ladder or a long gentle ramp to the same height stores the same mgh. The ramp just needs a smaller force over a longer distance.