Question

A cylinder rolls down an inclined plane without slipping as shown. The work done against friction during rolling motion is (a) always positive (b) always negative (c) zero (d) first positive and then negative​

Answer 1

There is no displacement by force in case of rolling it is friction. Only in case of rolling with sliding, friction does work.

Work done by pure rolling is always zero.

Hence option (c) zero is correct.

Answer 2

The work done against friction during rolling motion is zero.

• In rolling friction, the body rotates about its own axis.
• Due to this, the body returns to its initial position after every rotation.
• The cylinder rolls without slipping and if the cylinder had slipped, the friction would not have been zero.
• Pricisely, if slipping took place, work wouldn't have been zero either, because displacement is occuring.
• This means that the displacement is zero in case of rolling and hence, the friction is absent.
• Therefore, the work done against friction while rolling will be zero.