Answer: Forces from all shell mass cancel inside due to symmetry.
- A The total mass of the shell is negligible compared to the test point
- B Forces from all shell mass cancel inside due to symmetry
- C Gravity acts as a repulsive force for any point inside the shell
- D The mass density at every interior point of the shell is zero
Correct answer: B. Forces from all shell mass cancel inside due to symmetry
Explanation: Inside a uniform spherical shell, gravitational contributions from all parts of the shell cancel by symmetry. This is the shell theorem.
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.