Answer: 22.4 km/s.
- A 22.4 km/s
- B 11.2 km/s
- C 5.6 km/s
- D 44.8 km/s
Correct answer: A. 22.4 km/s
Explanation: At constant density, escape velocity is proportional to the radius (v = R√(8πGρ/3)). Doubling R doubles it to 22.4 km/s.
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.