A force `F=50N` is applied at one end of a string, the other end of which is tied to a block of mass `10kg`. The block is free to move on a frictionless horizontal surface. Take initial instant as `theta=30^@` and final instant as `theta=37^@`. For the time between these two instants, answer teh following questions?

Net work done by the force F on the block is

Options

A. (a) `50/3J`
B. (b) `100/3J`
C. (c) `75J`
D. (d) None of these

Answer

B

Explanation

`l_1=(2)/(sin 30^@)=4m`, `l_2=(2)/(sin 37^@)=10/3m`
Displacement of point `P: l_1-l_2=4-10/3=2/3m`

Work done, `W=F(l_1-l_2)=50xx2/3=100/3J`