Question

Orbital radius of a planet is doubled; then its time period becomes


(a) 2 times

(b) Remains the same

(c) 4

1/3 times

(d) 1/41/3 times

Explain your answer.

Answer 1

As t^2 is proportional to r^3 when r is doubled then t becomes 2^3/2 of initial value.

This expression comes from Kepler's third law