Answer: 36,000 km.
- A 3,600 km
- B 36,000 km
- C 3,60,000 km
- D 360 km
Correct answer: B. 36,000 km
Explanation: A 24-hour orbit has radius about 42,000 km from the centre, which is roughly 36,000 km above the surface.
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.