Question

A body of mass m kg. starts falling from a point 2R above the earth’s surface. Its kinetic energy when it has fallen to a point ‘R’ above the earth’s surface [R-Radius of earth, M-Mass of earth, G-Gravitational constant]

(a) (1/2) [(GMm)/R]

(b) (1/6) [(GMm)/R]

(c) (2/3) [(GMm)/R]

(d) (1/3) [(GMm)/R]

Answer 1

Correct option (b) (1/6) [(GMm)/R]

Explanation

When body starts falling toward earth’s surface its potential energy decreases so kinetic energy increases. Increase in kinetic energy = Decrease in potential energy Final kinetic energy – Initial kinetic energy = Initial potential energy – Final potential energy Final kinetic energy – 0

∴Final kinetic energy