question_answer

A planet revolves around a massive star in a highly elliptical orbit. Is the angular momentum constant over the entire orbit?

Answer:

                A planet revolves around a star under the effect of the gravitational force, which is purely radial in nature. As radial component of a force does not contribute to torque, so the angular momentum of the planet remains unaffected.                 As           \[\tau =\frac{dL}{dt}=0,\] so \[L=\]constant.