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

Air of density $1.2 \, kg \, m^{-3}$ is blowing across the horizontal wings of an aeroplane in such a way that its speeds above and below the wings are $150 \, m \, s^{-1}$ and $100 \, m \, s^{-1}$,respectively. The pressure difference between the upper and lower sides of the wings is ........ $N \, m^{-2}$.

$A$ steady flow of a liquid of density $\rho$ is shown in the figure. At point $1$,the area of cross-section is $2A$ and the speed of flow of liquid is $\sqrt{2} \ m \ s^{-1}$. At point $2$,the area of cross-section is $A$. Between the points $1$ and $2$,the pressure difference is $100 \ N \ m^{-2}$ and the height difference is $10 \ cm$. The value of $\rho$ is (Acceleration due to gravity $= 10 \ m \ s^{-2}$) (in $kg \ m^{-3}$)

Explain the upward force (dynamic lift) acting on an airplane wing.

Prove Bernoulli's Principle.

In a horizontal tube,the water pressure changes by $1500 \text{ N m}^{-2}$ between points $A$ and $B$ as shown in the figure below. The cross-sectional areas at $A$ and $B$ of the tube are $40 \text{ cm}^2$ and $20 \text{ cm}^2$,respectively. Find the rate of flow of water through the tube.