potential energy sign

Question

Why is gravitational potential energy of two attracting masses negative?

RankGuru · Accepted Answer

1. **Reference Choice**: In physics, we arbitrarily choose gravitational potential energy to be zero at infinite separation ($r = \infty$).
2. **Bound State**: As masses come closer, gravity (an attractive force) does work. To bring them back to infinity, an external agent must supply energy (do positive work).
3. **Significance**: Any state requiring positive work to reach the 'zero' state must itself have a **negative energy** level.
4. **Physics Fact**: Negative energy indicates a bound system where the components are 'trapped' by each other's field.

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potential energy sign

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