Three liquids of densities $d, 2d$,and $3d$ are mixed in equal volumes. Then the density of the mixture is

Is pressure a scalar or a vector quantity? Explain.

Explain the specific density or relative density of a substance.

$A$ hollow sphere of radius $R$ is filled completely with an ideal liquid of density $\rho$. The sphere is moving horizontally with an acceleration $2g,$ where $g$ is the acceleration due to gravity. If the minimum pressure of the liquid is $P_0$,then what is the pressure at the centre of the sphere?

The volume of an air bubble is doubled as it rises from the bottom of a lake to its surface. The atmospheric pressure is $75 \, cm$ of mercury. The ratio of the density of mercury to that of lake water is $\frac{40}{3}$. The depth of the lake in metres is:

Mountaineers suffer from nose bleeding (epistaxis) at higher altitudes. Explain.