Gravitational potential energy
The energy stored in the gravitational field due to the separation of masses. For two point masses M and m separated by distance r: E_p = -GMm/r. The negative sign reflects that energy must be added to separate the masses (move them to infinite separation).
Formula
E_p = −GMm/r
Real World
The Parker Solar Probe gained kinetic energy as it fell toward the Sun from 1 AU, converting negative gravitational potential energy into speed — reaching over 690,000 km/h at perihelion, the fastest human-made object ever.
Exam Focus
Always explain why E_p is negative: zero is defined at infinity, so bound systems have less energy — state this explicitly in 'explain' questions.
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