Question

An object is placed at a depth d below Earth's surface. Which mass contributes to the gravitational force acting on it?

Options

• The total mass of the entire Earth

• The mass of the shells above the object only

• The mass of the inner sphere of radius (R − d)

• The mass of the shells at exactly depth d

Answer 1

The mass of the inner sphere of radius (R − d)

Explanation:

At depth d, the inner sphere of radius (R − d) is the only mass that exerts a gravitational pull on the object. The outer shells, by the Shell Theorem, produce zero net force on objects inside them.