Question

The gravitational force exerted by earth on a particle as it travels from the earth’s surface towards the core

• A. increases
• B. is zero
• C. decreases
• D. remains same

Hint:

Inside Earth: - $g \propto r$ - Maximum at surface, zero at center

Answer 1

The Correct Option is C

Concept: Inside the Earth, the gravitational force acting on a particle is due only to the mass enclosed within the radius at that point. According to Newton’s shell theorem, outer layers do not contribute to the gravitational force.

Step 1: Gravitational force inside Earth.
At a distance $r$ from the center: \[ F \propto r \] Thus, force decreases linearly as we move towards the center.

Step 2: Behavior from surface to center.

• At surface ($r = R$): Force is maximum
• As $r$ decreases: Force decreases
• At center ($r = 0$): Force becomes zero

Step 3: Final conclusion.
Hence, as the particle moves from the surface to the core, the gravitational force: \[ decreases \]