Question

A man of mass m starts falling towards a planet of mass M and radius R. Inside the planet, which consists of a spherical shell of mass 2M/3 and a point mass M/3 at centre, the change in gravitational force experienced by the man is:

• A. 2GMm3R²
• B. 0
• C. GMm3R²
• D. 4GMm3R²

Hint:

Inside a spherical shell, gravitational force is zero.

Answer 1

The Correct Option is A

Step 1: Shell theorem.
Spherical shell exerts zero force inside.
Step 2: Only central mass acts.
Effective mass inside = M/3
Step 3: Change in force.
Difference gives (2GMm)/(3R²)