In the previous problem,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 of mercury in the two arms (in $; cm$)? (Specific gravity of mercury $= 13.6$)

Explain why:
$(a)$ The blood pressure in humans is greater at the feet than at the brain.
$(b)$ Atmospheric pressure at a height of about $6 \; km$ decreases to nearly half of its value at sea level,though the height of the atmosphere is more than $100 \; km$.
$(c)$ Hydrostatic pressure is a scalar quantity even though pressure is force divided by area.

In making an alloy,a substance of specific gravity $s_1$ and mass $m_1$ is mixed with another substance of specific gravity $s_2$ and mass $m_2$. Then,the specific gravity of the alloy is:

Two cylindrical vessels $A$ and $B$ of different areas of cross-section kept on the same horizontal plane are filled with water to the same height. If the volume of water in vessel $A$ is $3$ times the volume of water in vessel $B$,then the ratio of the pressures at the bottom of the vessels $A$ and $B$ is

In the arrangement shown, both the vessels $A$ and $B$ are identical, but the amount of water in $B$ is double that in $A$. The vessels are closed by identical leak-proof pistons at the same height. The pistons are connected to the ends of a lever arm. There is no friction between the pistons and the container walls. The system is in equilibrium in the situation shown. Now, the valve in the horizontal tube connecting both the vessels is opened. In which direction will the water flow through the tube?

Liquid is ...... while gas is ...... . (Fill in the blank) [incompressible,compressible]