JEE MainPhysicsGravitationMCQ+4 / −1
A satellite is in an elliptical orbit around a planet P. It is observed that the velocity of the satellite when it is farthest from the planet is 6 times less than that when it is closest to the planet. The ratio of distances between the satellite and the planet at closest and farthest points is:
- A1 : 2
- B1 : 3
- C1 : 6
- D3 : 4
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Correct answer: C
- Identify the two special points in the elliptical orbit
For a satellite moving in an elliptical orbit around a planet:
- At the closest point (perigee), distance from planet is minimum, say , and speed is maximum, say .
- At the farthest point (apogee), distance from planet is maximum, say , and speed is minimum, say .
Given: so,
- Use conservation of angular momentum
For motion under a central force, angular momentum is conserved.
At closest and farthest points, velocity is perpendicular to radius vector, so angular momentum magnitude is:
Hence, Cancelling ,
Substitute :
Cancel :
Therefore,
- Match with the given options
The required ratio of distances at closest and farthest points is:
So the correct option is C.
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