In a test experiment on a model aeroplane in a wind tunnel,the flow speeds on the upper and lower surfaces of the wings are $70 \,m/s$ and $65 \,m/s$ respectively. If the wing area is $2 \,m^2$,the lift of the wing is . . . . . . $N$. (Given density of air $= 1.2 \,kg/m^3$)

Why is it dangerous to stand on the edge of a platform near the tracks when a train is passing at high speed? Explain.

Water from a tap emerges vertically downwards with an initial speed of $1.0\,ms^{-1}.$ The cross-sectional area of the tap is $10^{-4}\,m^2.$ Assume that the pressure is constant throughout the stream of water and that flow is streamlined. The cross-sectional area of the stream,$0.15\,m$ below the tap would be: (take $g = 10\,ms^{-2}$ )

If the velocity of flow is $4 \, m/s$,then the velocity head is ......... $m$.

An $L$-shaped glass tube is just immersed in flowing water as shown. If the speed of the water current is $V$,then the height $h$ up to which the water rises will be

Consider a cylindrical tank of radius $1\,m$ filled with water. The top surface of the water is at $15\,m$ from the bottom of the cylinder. There is a hole on the wall of the cylinder at a height of $5\,m$ from the bottom. $A$ force of $5 \times 10^{5}\,N$ is applied on the top surface of the water using a piston. Calculate the speed of efflux from the hole. (Given: atmospheric pressure $P_{A} = 1.01 \times 10^{5}\,Pa$,density of water $\rho_{w} = 1000\,kg/m^{3}$,and gravitational acceleration $g = 10\,m/s^{2}$) (in $,m/s$)