Density of ice is $\rho$ and that of water is $\sigma$. What will be the decrease in volume when a mass $M$ of ice melts?

$A$ $U$-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 $0.8$.)

Explain the hydrostatic paradox.

At every point of a liquid at rest,the tangential stress is zero. Explain with reason.

What is $1$ Torr pressure? And what is $1$ bar?

The Sun is a hot plasma (ionized matter) with its inner core at a temperature exceeding $10^{7} \; K$,and its outer surface at a temperature of about $6000 \; K$. At these high temperatures,no substance remains in a solid or liquid phase. In what range do you expect the mass density of the Sun to be,in the range of densities of solids and liquids or gases? Check if your guess is correct from the following data: mass of the Sun $= 2.0 \times 10^{30} \; kg$,radius of the Sun $= 7.0 \times 10^{8} \; m$.