Question

A block of mass M is hanging over a smooth and light pulley through a string. The other end of a string is pulled by a constant force F. The kinetic energy of the block increases by 20J in 1 sec.
(1) the tension in string is Mg
(2) the tension in string is F
(3) the work done by the tension on the block is 20J in the above 1 sec.
(4) the work done by the force of gravity is-20J in above 1 sec