Assertion: If there are no external forces, the center of mass of a double star moves like a free particle.
Reason: If we go to the center of mass frame, then we find that the two stars are moving in a circle about the center of mass, which is at rest.

Options

A. If both assertion and reason are true and reason is the correct explanation of assertion.
B. If both assertion and reason are true but reason is not the correct explanation of assertion
C. If assertion is true but reason is false.
D. If both assertion and reason are false.

Answer

B

Explanation

In our frame of reference, the trajectories of the stars are a combination of
(i) uniform motion in a straight line of the centre of mass and
(ii) circular orbits of the stars about the centre of mass.