Gravitational Work in Elliptical Orbit – Rankers Physics

Planet and Satellite: Practice Problem & Solution

Assertion (A): Comets move around the sun in elliptical orbits. The gravitational force on the comet due to sun is not normal to the comet's velocity but the work done by the gravitation force over every complete orbit of the comet is zero. Reason (R): Gravitational force is a conservative force.  
(1) Both (A) & (R) are true and the (R) is the correct explanation of the (A)
(2) Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
(3) (A) is true but (R) is false
(4) Both (A) and (R) are false

Short Solution (Best for NEET):

To solve this problem, we apply the core principles of Planet and Satellite. Understanding the underlying formula is key to arriving at the correct answer below:

Gravitational force is a conservative force. For a conservative force, the work done over a closed path (like a complete elliptical orbit) is zero.

Therefore, both Assertion and Reason are true, and Reason is the correct explanation of the Assertion.

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