JEE Advanced · Physics · 9. Gravitation

A planet of mass M, has two natural satellites with masses $m_{1} a n d m_{2}$ . The radii of their circular orbits are $R_{1} a n d R_{2}$ respectively. Ignore the gravitational force between the satellites. Define $v_{1}, L_{1}, K_{1} a n d T_{1}$ to be, respectively, the orbital speed, angular momentum, kinetic energy and time period of revolution of satellite $1; a n d v_{2}, L_{2}, K_{2} a n d T_{2}$ and to be the corresponding quantities of satellite 2. Given $m_{1} / m_{2} = 2 a n d R_{1} / R_{2} = \frac{1}{4}$ , match the ratios in List-I to the numbers in List-II.

LIST -I LIST-II

A) $\frac{v_{1}}{v_{2}}$ P) $\frac{1}{8}$

B) $\frac{L_{1}}{L_{2}}$ Q) 1

C) $\frac{K_{1}}{K_{2}}$ R) 2

D) $\frac{T_{1}}{T_{2}}$ S) 8

A a-p;b-q;c-s;d-r;
B a-s;b-p;c-r;d-q;
C a-s;b-q;c-r;d-p;
D a-r;b-q;c-s;d-p;

Verified Solution

Answer & Solution

Correct Answer

(D) a-r;b-q;c-s;d-p;

Step-by-step Solution

Detailed explanation

\begin{matrix} \frac{m_{1}}{m_{2}} = 2 \\ \frac{R_{1}}{R_{2}} = \frac{1}{4} \end{matrix}\}

given

\frac{G M m_{1}}{R_{1}^{2}} = \frac{m_{1} V_{1}^{1}}{R_{1}}

v_{1}^{2} = \frac{G M}{R_{1}}, v_{2}^{2} = \frac{G M}{R_{2}}

\frac{v_{1}^{2}}{v_{2}^{2}} = \frac{R_{2}}{R_{1}} = 4

(i)

\frac{v_{1}}{v_{2}} = 2

(i i)

L = m v R

\frac{L_{1}}{L_{2}} = \frac{m_{1} v_{1} R_{1}}{m_{2} v_{2} R_{2}} = 2 \times 2 \times \frac{1}{4} = 1

(i i i)

K = \frac{1}{2} m v^{2}

\frac{K_{1}}{K_{2}} = \frac{m_{1} v_{1}^{2}}{m_{2} v_{2}^{2}} = 2 \times {(2)}^{2} = 8

(i v)

T = 2 π R / V

\frac{T_{1}}{T_{2}} = \frac{R_{1}}{v_{1}} \times \frac{v_{2}}{R_{2}} = \frac{R_{1}}{R_{2}} \times \frac{v_{2}}{v_{1}} = \frac{1}{4} \times \frac{1}{2} = \frac{1}{8}

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.

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	LIST -I		LIST-II
A)	$\frac{v_{1}}{v_{2}}$	P)	$\frac{1}{8}$
B)	$\frac{L_{1}}{L_{2}}$	Q)	1
C)	$\frac{K_{1}}{K_{2}}$	R)	2
D)	$\frac{T_{1}}{T_{2}}$	S)	8