Water flows through the tube shown. The cross-sectional areas of the wide and narrow parts are $5 \text{ cm}^2$ and $2 \text{ cm}^2$,respectively. The rate of flow is $500 \text{ cm}^3/\text{s}$. Find the difference in the mercury level of the $U$-tube in $\text{cm}$.

Water is flowing through a horizontal pipe in streamline flow. At the narrowest part of the pipe,

$A$ horizontal pipe carries water in a streamline flow. At a point along the pipe, where the cross-sectional area is $A_1$, the velocity of water is $V_1$ and the pressure is $P_1$. What is the pressure of water at another point where the cross-sectional area is $A_2$?

What is a venturi-meter? Explain its construction and working.

Glycerine of density $1.25 \times 10^3 \, kg \, m^{-3}$ is flowing through a conical section of a pipe. The area of cross-section of the pipe at its ends is $10 \, cm^2$ and $5 \, cm^2$, and the pressure drop across its length is $3 \, N \, m^{-2}$. The rate of flow of glycerine through the pipe is $x \times 10^{-5} \, m^3 \, s^{-1}$. The value of $x$ is $..............$.

Water is flowing through a horizontal tube having cross-sectional areas of its two ends as $A$ and $A'$ such that the ratio $A/A'$ is $5$. If the pressure difference of water between the two ends is $3 \times 10^5 \, N \, m^{-2}$,the velocity of water with which it enters the tube will be ......... $m \, s^{-1}$ (neglect gravity effects).