Gravitational Potential Energy Explained
Gravitational potential energy (GPE) is the energy stored in an object due to its position in a gravitational field — specifically its height above a reference level. The higher an object is lifted, the more potential energy it stores. This energy can be converted to kinetic energy when the object falls. GPE is fundamental to hydroelectric power, roller coasters, pile drivers, and gravitational potential wells in astrophysics.
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Formula
Gravitational Potential Energy
Calculate the gravitational potential energy of an object at height h (PE = mgh).
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Worked Example
Given:
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FAQs
What is the reference level for height?
Height h is measured from a reference level that you define — typically the ground, table top, or any convenient zero point. GPE is relative, not absolute. Only changes in GPE matter physically. What counts as 'zero height' depends on the problem context.
How does GPE relate to hydroelectric power?
Hydroelectric dams store water at height, converting it to gravitational potential energy. When water flows down through turbines, GPE converts to kinetic energy of moving water, then to rotational energy of turbines, then to electrical energy. The power output = mgh × flow rate × efficiency.
What happens to potential energy when an object falls?
As an object falls, height decreases so GPE decreases. By conservation of energy, this lost GPE converts to kinetic energy (in the absence of air resistance): mgh = ½mv². This gives the velocity at any height during free fall: v = √(2gh).