3. Explain why the value of g is zero at the centre of the earth.

Ans. : i. From the Newtonian view, we know that gravity is force exerted by everything that has mass. This means that the gravitational field from the Earth is not only from the centre, it is the sum of all the particles, molecules, or atoms that makes up the Earth. The acceleration due to gravity (g) on earth’s surface is given as

The value of g depends on the mass M of the earth and the radius R of the earth.

ii. As we go inside the earth, our distance from the centre of the earth decreases and no longer remains equal to the radius of the earth (R).

iii. Along – with the distance, the part of the earth which contributes towards the gravitational force felt also decreases, decreasing the value of (M).

iv. Due to combined result of change in R and M, value of g becomes zero at the centre of the earth.