Easy MCQ +4 / -1 PYQ · JEE Mains 2022

Two planets A and B of equal mass are having their period of revolutions TA and TB such that TA = 2TB. These planets are revolving in the circular orbits of radii rA and rB respectively. Which out of the following would be the correct relationship of their orbits?

  1. A $2r_A^2 = r_B^3$
  2. B $r_A^3 = 2r_B^3$
  3. C $r_A^3 = 4r_B^3$ Correct answer
  4. D $T_A^2 - T_B^2 = {{{\pi ^2}} \over {GM}}\left( {r_B^3 - 4r_A^3} \right)$

Solution

<p>${T_A} = 2{T_B}$</p> <p>Now $T_A^2 \propto r_A^3$</p> <p>$$ \Rightarrow {\left( {{{{r_A}} \over {{r_B}}}} \right)^3} = {\left( {{{{T_A}} \over {{T_B}}}} \right)^2}$$</p> <p>$\Rightarrow r_A^3 = 4r_B^3$</p>

About this question

Subject: Physics · Chapter: Gravitation · Topic: Kepler's Laws

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