Answer: GMm/(2r).
- A GMm/r
- B GMm/(2r)
- C -GMm/(2r)
- D GMm/2r
Correct answer: B. GMm/(2r)
Explanation: Binding energy = -total energy = -(-GMm/(2r)) = GMm/(2r). It represents the energy needed to free the satellite.
g is maximum at Earth's surface; going up, it falls off as 1/r² (inverse-square); going down, it falls off linearly with depth (since only the mass enclosed within radius r contributes), reaching zero at the centre.
Concept context
Universal gravitation, orbital mechanics, gravitational potential, and escape velocity.