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 periods, $T$ 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

The correct option is A $a^3$

Kepler's third law:

Square of the time period $T$ is directly proportional to cube of semi-major axis $a$ i.e $T^2\propto a^3$