Q. A planet is revolving round the sun in an elliptical orbit. The work done on the planet by the gravitational force of sun is zero:

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A

In some parts of the orbit

B

In any part of the orbit

C

In no part of the orbit

D

In one complete revolution

Solution:

In elliptical orbit at the positions of aphelion and perihelion points the velocity of planet is perpendicular to the position vector so for small displacements at these points work done by gravitational force of sun is zero and in one complete revolution of planet it is also zero as gravitational field is a conservative field.

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