$A$ uniform meter scale balances at the $40\,cm$ mark when weights of $10\,g$ and $20\,g$ are suspended from the $10\,cm$ and $20\,cm$ marks. The weight of the meter scale is ...... $g$.

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

$A$ heavy iron bar of mass $12 \,kg$ has one end on the ground and the other on the shoulder of a man. The rod makes an angle $60^{\circ}$ with the horizontal. The weight experienced by the man is:

$A$ rod of weight $W$ is supported by two parallel knife edges $A$ and $B$ and is in equilibrium in a horizontal position. The knives are at a distance $d$ from each other. The centre of mass of the rod is at distance $x$ from $A.$ The normal reaction on $A$ is

$A$ weightless rod is acted on by upward parallel forces of $2N$ and $4N$ at ends $A$ and $B$ respectively. The total length of the rod $AB = 3m$. To keep the rod in equilibrium,a force of $6N$ should act in the following manner:

Two persons of equal height are carrying a long uniform wooden beam of length $\ell$. They are at a distance of $\frac{\ell}{5}$ and $\frac{\ell}{3}$ from the nearest ends of the rod. The ratio of the normal reaction at their heads is