Question

A system is shown in the figure. A man standing on the block is pulling rope. Velocity of the point of string in contact with the hand of man is 2 m/s downwards. The velocity of the block in m/s will be [assume that the block does not rotate]

Answer 1

As in figure
$l_1+l_2+l_3+l_4=C$

$\frac{d{l}_1}{dt}+\frac{d{l}_2}{dt}+\frac{d{l}_3}{dt}+\frac{d{l}_4}{dt}=0$
$-v-v+0+v+2=0$
$v=2\text{m/s}$