Answer: 4:1.
- A 2:1
- B 4:1
- C 8:1
- D 16:1
Correct answer: B. 4:1
Explanation: T2 proportional to r3 (Kepler). (T1/T2)2 = (r1/r2)3. (8)2 = (r1/r2)3. 64 = (r1/r2)3. r1/r2 = 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.