The figure represents vertical sections of four wings moving horizontally in air. In which case is the force upwards?

Prove Bernoulli's Principle.

$A$ horizontal pipe carries water in a streamlined flow. At a point along the pipe,where the cross-sectional area is $10 \text{ cm}^2$,the velocity of water is $1 \text{ ms}^{-1}$ and the pressure is $2000 \text{ Pa}$. What is the pressure of water at another point where the cross-sectional area is $5 \text{ cm}^2$ (in $Pa$)? [Density of water $= 1000 \text{ kgm}^{-3}$]

Water flows steadily through a horizontal pipe of variable cross-section. If the pressure of water is $P$ at a point where flow speed is $v$,the pressure at another point where the flow speed is $2v$,is (Take density of water as $\rho$)

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

If water is flowing in a pipe with speed $2 \, m/s$,then its kinetic energy per unit volume is ........... $J/m^3$.