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Gravitation question

2022 · 25 Jun · Shift 2 · Q68
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  5. /2022 · 25 Jun · Shift 2 · Q68

Gravitation question

2022 · 25 Jun · Shift 2 · Q68

JEE MainPhysicsGravitationNumerical+4 / −1
Two satellites S1 and S2 are revolving in circular orbits around a planet with radius R1 = 3200 km and R2 = 800 km respectively. The ratio of speed of satellite S1 to be speed of satellite S2 in their respective orbits would be 1x{1 \over x}x1​ where x = ‾\underline{\hspace{2cm}}​.
Numerical answer
View written solutionFree

Correct answer: 2

  1. Speed of a satellite in a circular orbit

For a satellite revolving around a planet in a circular orbit, the orbital speed is

v=GMrv = \sqrt{\frac{GM}{r}}v=rGM​​

where:

  • GGG = gravitational constant
  • MMM = mass of the planet
  • rrr = radius of the orbit from the center of the planet
  1. Apply to the two satellites

For satellite S1S_1S1​:

v1=GMR1v_1 = \sqrt{\frac{GM}{R_1}}v1​=R1​GM​​

For satellite S2S_2S2​:

v2=GMR2v_2 = \sqrt{\frac{GM}{R_2}}v2​=R2​GM​​

  1. Take the ratio

v1v2=GM/R1GM/R2=R2R1\frac{v_1}{v_2} = \sqrt{\frac{GM/R_1}{GM/R_2}} = \sqrt{\frac{R_2}{R_1}}v2​v1​​=GM/R2​GM/R1​​​=R1​R2​​​

Given:

R1=3200 km,R2=800 kmR_1 = 3200\text{ km}, \quad R_2 = 800\text{ km}R1​=3200 km,R2​=800 km

So,

v1v2=8003200=14=12\frac{v_1}{v_2} = \sqrt{\frac{800}{3200}} = \sqrt{\frac{1}{4}} = \frac{1}{2}v2​v1​​=3200800​​=41​​=21​

  1. Compare with the form given

It is given that

v1v2=1x\frac{v_1}{v_2} = \frac{1}{x}v2​v1​​=x1​

Thus,

1x=12  ⟹  x=2\frac{1}{x} = \frac{1}{2} \implies x = 2x1​=21​⟹x=2

Final Answer

x=2x = 2x=2

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