In an experiment with a beam balance on unknown mass $m$ is balanced by two known mass $m$ is balanced by two known masses of $16\, kg$ and $4\, kg$ as shown in figure. The value of the unknown mass $m$ is ....... $kg$.

The left end of a massless stick with length $l$ is placed on the corner of a table, as shown in Fig. A point mass $m$ is attached to the center of the stick, which is initially held horizontal. It is then released. Immediately afterward, what normal force does the table exert on the stick?

A metre stick is balanced on a knife edge at its centre. When two coins, each of mass $5\; g$ are put one on top of the other at the $12.0 \;cm$ mark, the stick is found to be balanced at $45.0\; cm$. What is the mass of the metre stick?

In a physical balance working on the principle of moments, when $5\, mg$ weight is placed on the left pan, the beam becomes horizontal. Both the empty pans of the balance are of equal mass. Which of the following statements is correct?

Two men are carrying a uniform bar of length $L$, on their shoulders. The bar is held horizontally such that younger man gets $(1/4)^{th}$ load. Suppose the younger man is at the end of the bar, what is the distance of the other man from the end

The spool shown in figure is placed on rough horizontal surface and has inner radius $r$ and outer radius $R$. The angle $\theta$ between the applied force and the horizontal can be varied. The critical angle $(\theta )$ for which the spool does not roll and remains stationary is given by