Question

A boy tied a string to one of the ends of a box and started sliding the box on a playground. He then observed a circular track and rushed there and completed half revolution of the track with his box. The work done by friction on the box is _____.

• A. Non- zero
• B. Zero
• C. 4 J
• D. Can't be said

Answer 1

The correct option is A

Non- zero

When box slides on the ground, friction will act on the box opposite to the direction of motion. Even on the circular track, if we take any small portion, friction is always opposite to the displacement. Hence work done by the friction =- force $\times$ displacement. Therefore, the work done by friction on the toy is negative work.