Answer: the planet mass and radius.
- A the mass of the projectile
- B the launch direction
- C the projectile shape
- D the planet mass and radius
Correct answer: D. the planet mass and radius
Explanation: Escape velocity v<sub>e</sub> = √(2GM/R) depends only on the planet mass M and radius R, not on the projectile.
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.