$A$ 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 $g = 9.8 \; m/s^{2}$).

An aeroplane of mass $4.5 \times 10^4 \,kg$ and total wing area of $600 \,m^2$ is travelling at a constant height. The pressure difference between the upper and lower surfaces of its wings is (Acceleration due to gravity $= 10 \,m \,s^{-2}$)

$A$ liquid flows through a horizontal tube. The velocities of the liquid in the two sections which have areas of cross-section $A_1$ and $A_2$ are $v_1$ and $v_2$ respectively. The difference in the levels of the liquid in the two vertical tubes is $h$. The incorrect statement is

The venturi-meter works on:

An ideal fluid of density $800 \; kg \cdot m^{-3}$ flows smoothly through a bent pipe (as shown in the figure) that tapers in cross-sectional area from $a$ to $\frac{a}{2}$. The pressure difference between the wide and narrow sections of the pipe is $4100 \; Pa$. At the wider section,the velocity of the fluid is $\frac{\sqrt{x}}{6} \; m \cdot s^{-1}$. Find the value of $x$. (Given $g = 10 \; m \cdot s^{-2}$)

The lift of an airplane is based on