$250 \; N$ force is required to raise a $75 \; kg$ mass using a pulley system. If the rope is pulled by $12 \; m$ and the load is lifted by $3 \; m$,the efficiency of the pulley system will be ......$\%$

$A$ frictionless pulley is attached to one arm of a balance and a string passed around it carries two masses $m_1$ and $m_2$. The pulley is provided with a clamp due to which $m_1$ and $m_2$ do not move with respect to each other. On removing the clamp,$m_1$ and $m_2$ start moving. How much change in counter mass has to be made to restore balance?

As shown in the figure,two equal masses each of $2\, kg$ are suspended from a spring balance. The reading of the spring balance will be ......... $kg$.

Two masses $2 \, kg$ and $3 \, kg$ are attached to the ends of a string passed over a pulley fixed at the top. The tension and acceleration are:

Two masses of $5 \ kg$ and $10 \ kg$ are suspended from a massless pulley as shown in the figure. Calculate the acceleration of the system when the masses are left free.

$A$ uniform metal chain of mass $m$ and length $L$ passes over a massless and frictionless pulley. It is released from rest with a part of its length $l$ hanging on one side and the rest of its length $L - l$ hanging on the other side of the pulley. At a certain point in time,when $l = \frac{L}{x}$,the acceleration of the chain is $\frac{g}{2}$. The value of $x$ is ........