Answer: 4.
- A 2
- B 4
- C 1/4
- D 16
Correct answer: B. 4
Explanation: Conservation of angular momentum: vp·rp = va·ra, so vp/va = ra/rp = 4.
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.