Question

What would be the period of a planet whose orbit has a semi major axis of 4 AU?

Answer 1

According to Kepler's Third Law,$P^{2}= D^{3}$  where P the period which is expressed in units of years and D which is the distance from the earth to the sun which is expressed in units of AU

Thus, $P=D^{3/2}$.For a planet that has $D=4 AU,P=(4)^{3/2}$

$\therefore(4\times4\times4)^{1/2}$

$= 8 years$