Question

let the period of revolution of a Planet at the distance R from a star be T prove that if it was a distance of 2R from the star its period of revolution will be √8 T

Answer 1

${t}^{2} = k {r}^{3}$
use this to find your answer

Answer 2

 T' = \sqrt{8} T Hence, time period will be \sqrt{8} T , when distance between planet and star will be 2R.