$A$ nurse measures the blood pressure of a seated patient to be $190 \,mm$ of $Hg$.

$A$ $U$-tube contains water and methylated spirit separated by mercury. The mercury columns in the two arms are initially in level with $10.0 \; cm$ of water in one arm and $12.5 \; cm$ of spirit in the other. If $15.0 \; cm$ of water and spirit each are further poured into the respective arms of the tube,what is the difference in the levels (in $cm$) of mercury in the two arms? (The specific gravity of spirit is $0.8$.)

Why are railway tracks laid on large-sized wooden sleepers?

Three liquids of densities $d$,$2d$,and $3d$ are mixed in equal proportions of weights. The relative density of the mixture is

Equal masses of water and a liquid of density $2 \ g/cm^3$ are mixed together. The density of the resulting mixture is ........ $g/cm^3$.

$A$ thin uniform tube is bent into a circle of radius $r$ in the vertical plane. Equal volumes of two immiscible liquids,whose densities are ${\rho _1}$ and ${\rho _2}$ $({\rho _1} > {\rho _2})$,fill half the circle. The angle $\theta$ between the radius vector passing through the common interface and the vertical is