Gravitational potential energy — Science definition

Stored energy an object has because of its height in a gravitational field: PE = mgh.

Where it is taught

In use

Gravitational potential energy is the energy an object stores simply by being up high, PE = mgh, where m is mass, g = 9.

Kinetic & Potential Energy

Questions using gravitational potential energy

Problem 1

Find the gravitational potential energy of a 0.50 kg ball held 20 m above the ground. (g = 9.8 m/s²)
Answer and explanation

98 J

PE = mgh = 0.50 × 9.8 × 20 = 98 J.

Problem 2

Explain why gravitational potential energy depends on the reference level you choose, and why that is not a problem in practice.
Answer and explanation

Because PE = mgh measures height h from a chosen zero level, the numerical value of PE changes if you pick a different reference. This is not a problem because only changes in PE (as an object rises or falls) affect motion, and those changes come out the same no matter where you place the reference level.

Problem 3

Explain the following claim and supply a valid example or counterexample: Gravitational potential energy needs a chosen reference; negative values can be valid.
Answer and explanation

U=mgh=58.8 J; changing the reference shifts absolute U but not energy differences. Gravitational potential energy needs a chosen reference; negative values can be valid.

Response criteria

  • State a scientifically accurate conclusion.
  • Show the calculation or mechanism that supports it.
  • Include units, conditions, or limits where relevant.

Problem 4

Find the gravitational potential energy of a 2.0 kg object 5.0 m above the ground. (g = 9.8 m/s²)
Answer and explanation

98 J

PE = mgh = 2.0 × 9.8 × 5.0 = 98 J.

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