The blades of a windmill sweep out a circle of area $A$. If the wind flows at a velocity $v$ perpendicular to the circle,then the mass of the air of density $\rho$ passing through it in time $t$ is

An incompressible fluid flows steadily through a cylindrical pipe which has radius $2r$ at point $A$ and radius $r$ at point $B$ further along the flow direction. If the velocity at point $A$ is $v$,what is its velocity at point $B$?

Water is moving with a speed of $5.18 \; ms^{-1}$ through a pipe with a cross-sectional area of $4.20 \; cm^2$. The water gradually descends $9.66 \; m$ as the pipe increases in area to $7.60 \; cm^2$. The speed of flow at the lower level is ....... $ms^{-1}$.

Which of the following is not a characteristic of turbulent flow?

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

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 ........ $mm/s$.