Question

In which situations is gravitational potential energy present? Check all that apply.

A person walks up a flight of stairs.
A person runs across a room.
Wind blows against a steel table anchored to the ground.
Wind lifts a balloon into the air.
A weightlifter holds a barbell on the ground.
A weightlifter holds a barbell straight overhead.

Answer 1

Select A, D, and F.

Reason: Gravitational potential energy depends on an object's height in a gravitational field.
- A (walking up stairs): yes — the person's center of mass rises, increasing GPE.
- D (wind lifts a balloon): yes — the balloon is raised, so it gains GPE.
- F (barbell overhead): yes — the barbell is elevated, so it has GPE.

The others are not intended to have (additional) gravitational potential energy in this context:
- B (running across a room): no — height doesn't change.
- C (wind on an anchored table): no — taken relative to the ground, there's no change (and in typical problems the table is treated as at the reference level).
- E (barbell on the ground): no — taken as the zero reference for GPE.

(If you choose a different zero reference height, every elevated object technically has GPE; the answers above use the usual ground/reference conventions.)