Work Done by Muscles – Rankers Physics

Potential Energy & Equilibrium: Practice Problem & Solution

Assertion (A): Karnam Malleshwari famous Indian weight lifter lifts a weight up and returns it to same initial position along the same path. Net work done by muscles of weight lifter is positive. Reason (R): Net displacement of weight is zero.  
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 Potential Energy & Equilibrium. Understanding the underlying formula is key to arriving at the correct answer below:

Reason (R) is true as the weight returns to its starting point, making net displacement zero.

Assertion (A) is considered true in a physiological sense, as muscles expend energy. However, zero net displacement (R) implies zero net mechanical work on the weight by gravity, and thus zero net mechanical work by muscles if there is no change in kinetic energy. Therefore, (R) does not explain (A).

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