NEET Physics Question - Work Energy and Power - Work Done by Constant and Variable Forces

Assertion (A): Work done is positive when force acts in the direction of displacement.

Reason (R): Work done by frictional force can not be positive.

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:

Work is \(W = \vec{F} \cdot \vec{d} = Fd cos\theta\). If \(theta = 0\), \(W\) is positive, so (A) is true. Frictional force always opposes motion, so work done by it is negative or zero, never positive. So (R) is true. However, (R) does not explain (A).

Rankers Physics

Work Direction and Friction

Solution:

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