Find the mechanical advantage for pulling mass $M$ by the person as shown in the figure.

$A$ pulley fixed to the ceiling carries a string with blocks of mass $m$ and $3m$ attached to its ends. The masses of the string and pulley are negligible. When the system is released,what is the acceleration of its centre of mass?

Three identical blocks of masses $m = 2\; kg$ are pulled by a force $F = 10.2\; N$ with an acceleration of $0.6\; m/s^2$ on a frictionless surface. What is the tension (in $N$) in the string between the blocks $B$ and $C$?

At what value of $m_1$ will the $8\, kg$ mass be at rest?

$A$ boy is hanging from the branch of a tree as shown. For the tension in his arms to be maximum,the angle between his arms must be ............ $^o$.

In the pulley system shown, the mass of the ball is $1.2$ times greater than the mass of the rod. The length of the rod is $50 \,cm$. The ball is set on the same level as the lower end of the rod and then released. What is the acceleration of the rod with which it comes down (in $\,m/s^2$)? Assume the pulleys and threads are massless and friction is neglected. (Use $g = 10 \,m/s^2$)