Question

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 20 J in 1s.

• A. The tension in the string is Mg.
• B. The tension in the string is F.
• C. The work done by the tension on the block is 20 J in the above 1 s.
• D. The work done by the force of gravity is - 20 J in the above 1 s.

Answer 1

The correct option is B The tension in the string is F.


As tension is same throughout a mass less string
tension = F
As per work enough theorem work done by all focus (F and weight)
$=\Delta KE=20J$