Work Done Against Gravity with Uniform Velocity – Rankers Physics

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

Assertion (A): A man carrying a load on his head and walking with uniform velocity on a street does not work against gravity. Reason (R): When a body moves with uniform velocity, work done by all forces on this body is zero.  
(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 Work Done by Constant and Variable Forces. Understanding the underlying formula is key to arriving at the correct answer below:

Assertion (A) is true because the displacement (horizontal) is perpendicular to the gravitational force (vertical), so work done \(W = \vec{F} \cdot \vec{d} = Fd \cos(90^{circ}) = 0\).

Reason (R) is also true by the Work-Energy Theorem for uniform velocity. However, (R) does not explain (A).

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