Answer: density.
- A mass
- B density
- C radius
- D temperature
Correct answer: B. density
Explanation: For a surface-grazing orbit T = √(3π/Gρ), which depends only on the mean density ρ of the planet.
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.