question_answer

Statement I Work done by static friction could be negative.

Statement II When static friction acts on a body that body must have zero KE.

A)  Both Statement I and Statement II are true and the Statement II is the correct explanation of the Statement I

B)  Both Statement I and Statement II are true but the Statement II is not the correct explanation of the Statement I

C)  Statement I is true but Statement II is false

D)  Both Statement I and Statement II are false

Correct Answer: C

Solution :

 Idea If static friction acts on a body, it might be at rest or in motion. Work done by static friction could be negative or positive or zero. Statement I is true but the Statement II is false. If static friction acts on a body, the relative motion of the body with respect to the surface below must be zero. Consider example below The work done on box by \[{{f}_{s}}\]= positive work done by 4 on the bus floor = negative But here box has KE as it is in motion with the bus. TEST Edge In an accelerated frame, the person could move with the bus due to static friction only.