JEE Main 2021 · PhysicsMultiple choiceSingle correctMediumCalculation

JEE Main 24 February 2021, Shift 1, Physics Q2

Question 2 of 90 in this shift, Physics question 2 of 30, Section A.

Two stars of masses m and 2m at a distance d rotate about their common centre of mass in free space. The period of revolution is :

(1) $\frac{1}{2\pi}\sqrt{\frac{3Gm}{d^{3}}}$
(2) $2\pi\sqrt{\frac{d^{3}}{3Gm}}$ Official answer
(3) $2\pi\sqrt{\frac{3Gm}{d^{3}}}$
(4) $\frac{1}{2\pi}\sqrt{\frac{d^{3}}{3Gm}}$

Official answer

Option 2

NTA final key.

Chapter: Gravitation
Topic: Orbital Mechanics
Idea tested: Binary Star Systems

Same idea in other shifts

Asked 3× in all

15 Apr 2023, Shift 1 · Q36Two identical particles each of mass 'm' go round a circle of radius $a$ under the action of their mutual gravitational attraction. The…MediumSingle correct
3 Aug 2021, Shift 2 · Q26Two particles of equal mass 'm' go round a circle of radius $R$ under the action of their mutual gravitational attraction. The speed of…MediumNumerical value

Question text from the official JEE Main paper published by NTA; answer from the final answer key. Chapter, topic and idea tags, difficulty and skill are Lumi’s. Lumi analyses 108 of the 174 JEE Main shifts held from 2017 to 2026.