Question

The escape velocity for a planet is v_e. A tunnel is dug along a diameter of the planet and a small body is dropped into it at the surface. When the body reaches the centre of the planet, its speed will be 

(a)  v_e

(b) v_e/√2

(c) v_e/2

(d) Zero

Answer 1

Correct option(b) v_e/√2

Explanation:

Gravitational potential at the surface of the earth 

Gravitational potential at the centre of earth

By the conservation of energy