Question

What is the time taken by a planet to sweep an area of 2 million square km if the time taken by the same planet to cover an area of 1 million square km is 36 hours?

(a) 18 hours

(b) 36 hours

(c) 72 hours

(d) 144 hours

The question was posed to me at a job interview.

My question is based upon Gravitation topic in section Gravitation of Physics – Class 11

Answer 1

Correct answer is (c) 72 hours

Easiest explanation: According to Kepler’s law of area, a line segment joining a planet and the Sun sweeps out equal areas during equal intervals of time.

If it takes 36 hours to sweep an area of 1 million square km, it would take (36 + 36) hours to sweep an area of (1 + 1) million square km.

Therefore, the answer is 72 hours.