JEE MainPhysicsGravitation
Two satellites A and B of masses m and 3m respectively are to be placed in circular orbits around the Earth. If a student plots the expected orbital speed v against the orbital radius r for both satellites, which of the following correctly describes the resulting graphs?
Options
- ATwo distinct decreasing curves, where the curve for satellite B lies above the curve for satellite A.
- BA single coincident curve for both satellites, which decreases non-linearly and is concave upwards.
- CTwo distinct decreasing curves, where the curve for satellite B lies below the curve for satellite A.
- DA single coincident straight line for both satellites, having a negative slope.
Correct answer
B. A single coincident curve for both satellites, which decreases non-linearly and is concave upwards.
Step-by-step solution
The orbital speed of a satellite in a circular orbit is given by v = GM r , where M is the mass of the Earth and r is the orbital radius. This formula shows that the orbital speed is independent of the mass of the satellite. Therefore, both satellites A and B will have the exact same relationship between v and r , meaning their graphs will coincide into a single curve. Furthermore, the relationship is v r^ -1/2 . This represents a non-linear decreasing curve. Since d^2v dr^2 > 0 , the curve is concave upwards. Thus