Q 11-07-004NEETNEET 2025Top questionEasy
The radius of Martian orbit around the Sun is about $4$ times the radius of the orbit of Mercury. The Martian year is $687$ Earth days. Then which of the following is the length of $1$ year on Mercury ?
Answer: (A) $88$ earth days
Kepler's third law: $T \propto r^{3/2}$.
$$T_{\text{Mercury}} = T_{\text{Mars}}\left(\frac{1}{4}\right)^{3/2} = \frac{687}{8} \approx 86\ \text{days}$$
The closest option is $88$ Earth days.
Solution by Sreeraj P, M.Sc Physics