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PhysicsSingle correct+4 / -1Question 30 of 75

JEE Main 2026 · 2 Apr · Shift 1, Physics question 30

A planet (P1P_1) is moving around the star of mass 2M2M in the orbit of radius RR. Another planet (P2P_2) is moving around another star of mass 4M4M in a orbit of radius 2R2R. Ratio of time periods of revolution of P2P_2 and P1P_1 is ________.

Choose one option
Answer and worked solution

Official answer: B

Kepler's third law. T=2πr3GMT=2\pi\sqrt{\dfrac{r^3}{GM}}, so
T2T1=(2R)3/4MR3/2M=4=2.\frac{T_2}{T_1}=\sqrt{\frac{(2R)^3/4M}{R^3/2M}}=\sqrt4=2.

(B)