Air is blowing across the horizontal wings of an aeroplane in such a way that its speeds below and above the wings are $90\, m/s$ and $120\, m/s$ respectively. If the density of air is $1.3\, kg/m^3$,then the pressure difference between the lower and upper sides of the wings will be ........ $N/m^2$.

Obtain Bernoulli's equation for a fluid at rest.

The figure shows a liquid of given density flowing steadily in a horizontal tube of varying cross-section. The cross-sectional areas at $A$ is $1.5 \, cm^2$,and at $B$ is $25 \, mm^2$. If the speed of the liquid at $B$ is $60 \, cm/s$,then find $(P_A - P_B)$ in $Pa$. (Given: $P_A$ and $P_B$ are liquid pressures at points $A$ and $B$ respectively. Density $\rho = 1000 \, kg/m^3$. $A$ and $B$ are on the axis of the tube.)

An aeroplane of mass $3 \times 10^4 \, kg$ and total wing area of $120 \, m^2$ is in a level flight at some height. The difference in pressure between the upper and lower surfaces of its wings in kilopascals is $(g = 10 \, m/s^2)$.

The weight of an aeroplane flying in the air is balanced by:

$A$ plane is in level flight at constant speed and each of its two wings has an area of $25 \; m^{2}$. If the speed of the air is $180 \; km/h$ over the lower wing and $234 \; km/h$ over the upper wing surface,determine the plane's mass in $kg$. (Take air density to be $1 \; kg \; m^{-3}$ and $g = 9.8 \; m/s^{2}$).