Work by Tension in Circular Motion – Rankers Physics

Work Done by Constant and Variable Forces: Practice Problem & Solution

Assertion (A): A particle is rotated in a vertical circle with the help of a string. Work done by tension in the string on particle is zero. Reason (R): Tension is always perpendicular to instantaneous velocity.
Both (A) & (R) are true and the (R) is the correct explanation of the (A)
Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
(A) is true but (R) is false
Both (A) and (R) are false

Solution Explained:

To solve this problem, we apply the core principles of Work Done by Constant and Variable Forces. Understanding the underlying formula is key to arriving at the correct answer below:

In circular motion, tension acts as the centripetal force, directed towards the center, while velocity is tangential. Thus, tension is always perpendicular to velocity (\(\theta = 90^\circ\)), meaning work done (\(W = Fd cos 90^\circ\)) is zero. Both are true, and Reason explains Assertion.

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