Answer: One-fourth.
- A Double
- B Half
- C One-fourth
- D Four times
Correct answer: C. One-fourth
Explanation: F = Gm1m2/r2. If r doubles, F = Gm1m2/(2r)2 = F/4. Force becomes one-fourth.
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.