A monkey of mass m is balanced by a counterweight on the pulley AA monkey of mass m is balanced by a counterweight on the pulley A

Question

A monkey of mass m is balanced by a counterweight on the pulley A. Pulley A balances
a load on the opposite side of pulley B. The system is stationary. Rope and pulleys are
ideal.With what speed (in 1 ms ) will the block of mass 2m move, if the monkey start
climbing with a speed of 1 5 ms relative to the rope?

Answer 1

Dear Student,

As all the forces are balanced.
When monkey start climbing with the speed 8m/s with respect to the rope. So, rope has moved down by 8m/s. so both monkey and the the block of mass m has moved up by 4m/s. But as there is no external force, position of centre of mass should remain constant. As monkey and block of mass m combined mass 2m and are moving up by 4m/s so block of mass 2m should move down by 4m/s to keep centre of mass at same position.