Question

A planet revolves in an elliptical orbit around the sun. The semi-major and semi-minor axes are $a$ and $b$. Then the square of time period, $T$ is directly proportional to

• A. $a^3$
• B. $b^3$
• C. $\left(\frac{a+b}{2}\right)^{3}$
• D. $\left(\frac{a-b}{2}\right)^{3}$

Answer 1

Answer: (A)

The square of the period of planet is directly proportional to the cube of the semi-major axis of the elliptical orbit.
$\Rightarrow T^{2}\,\propto\,a^{3}$