Can two streamlines cross each other? Why?

The total area of cross-section is $0.25\,m^2$. If the blood is flowing at the rate of $100\,cm^3/s$,then the average velocity of flow of blood through the capillaries is ........ $mm/s$.

Explain streamline and streamline flow.

$A$ laminar stream is flowing vertically down from a tap of cross-section area $1 \ cm^2$. At a distance $10 \ cm$ below the tap,the cross-section area of the stream has reduced to $0.5 \ cm^2$. The volumetric flow rate of water from the tap is about ........ $litre/min$.

The surface of water in a water tank of cross-section area $750 \text{ cm}^2$ on the top of a house is $h \text{ m}$ above the tap level. The speed of water coming out through the tap of cross-section area $500 \text{ mm}^2$ is $30 \text{ cm/s}$. At that instant, $dh/dt$ is $y \times 10^{-3} \text{ m/s}$. The value of $y$ will be

Explain critical speed,white water rapids,and turbulent flow.