Question

A planet of mass M moves around the Sun along an ellipse so that its minimum distance from the Sun is equal to r and the maximum distance to R. Making use of Kepler s laws, find its period of revolution around the Sun.

Answer 1

Solution

Semi major axis $(\frac{r+R}{2}) =a$

According to kepler law time period is given by

$T=\frac{2\pi a^{3/2}}{\sqrt{ \gamma m_s}}$

$T=\pi\sqrt{\frac{(r+R) ^3}{2\gamma m_s}}$

Where m_s is mass of sun.