Question

Assertion (A): Even though a planet revolve around the sun in an elliptical orbit, the angular momentum of planet is constant.
Reason (R) : Any force other than mutual gravitational force is absent between the planet and the sun.

• A. Both A and R are true and R is correct explanation of A
• B. Both A and R are true and R is not correct explanation of A
• C. A is true and R is false
• D. A is false and R is true

Answer 1

Answer: (A)

Both A and R are true and R is correct explanation of A

Angular momentum of planet revolving around the sun is constant because the line of force of the gravitational force passes through the sun . Therefore torque about the sun is zero.
$\therefore$ Angular momentum will remain constant. And there is no other force acting on the planet, which results into zero tangential force.