I keep getting “Gravitational potential energy” questions wrong in Gravitation. What's the trap?
using mgh far from the surface, where it no longer holds.
The usual trap: using mgh far from the surface, where it no longer holds. How to avoid it: mgh is only the near-surface approximation of −GMm/r. Go back to the definition — for large distances PE = −GMm/r (negative, zero at infinity), not mgh.
Key point
Gravitational potential energy
Common mistake
using mgh far from the surface, where it no longer holds.
Memory tip
mgh is only the near-surface approximation of −GMm/r.
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