Question

State whether the given statement is True or False :

A block of mass $M$ is hanging over a smooth and light pulley through a light string. The other end of the string is pulled by a constant force $F$. The kinetic energy of the block increases by $40$ $J$ in $1$ $s$. The work done by the force of gravity is $40$ $J$ in the above $1$ $s$.

• A. True
• B. False

Answer 1

The correct option is B False

The work done by the tension in the block, that is the external force, is equal to the sum of gain in kinetic energy of the block and work done by block against the gravity.

However it cannot be commented upon the work done by gravity here since the mass of the block and hence the displacement of block against gravity is unknown.