Physics · Gravitation

NEET (UG) 2025 — Question 29

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 ?

Option A:
88 earth days
Correct
Option B:
225 earth days
Option C:
172 earth days
Option D:
124 earth days

Answer: A

Step-by-step solution

$\frac{T_{\text {Mercury }}}{T_{\text {Martian }}}=\left(\frac{r_{\text {Mercury }}}{r_{\text {Martian }}}\right)^{3 / 2}=\left(\frac{1}{4}\right)^{3 / 2}=\frac{1}{8}$

$\mathrm{T}_{\text {Mercury }}=\frac{\mathrm{T}_{\text {Martian }}}{8}=\frac{687}{8}=85.875$ days $\approx 88$ days

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Exam: NEET (UG) 2025
Paper: 2025 paper
Subject: Physics
Chapter: Gravitation
Topic: Planetary Motion & Binary Star System (Kepler's Law)

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Answer: A

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