An ideal liquid flows through a horizontal tube of variable diameter. The pressure is lowest where the . . . . . . .

$A$ fully loaded Boeing aircraft has a mass of $3.3 \times 10^{5} \; kg$. Its total wing area is $500 \; m^{2}$. It is in level flight with a speed of $960 \; km/h$.
$(a)$ Estimate the pressure difference between the lower and upper surfaces of the wings.
$(b)$ Estimate the fractional increase in the speed of the air on the upper surface of the wing relative to the lower surface. [The density of air is $\rho = 1.2 \; kg/m^{3}$]

Water from a tap emerges vertically downwards with an initial velocity of $4 \,m/s$. The cross-sectional area of the tap is $A$. The flow is steady and the pressure is constant throughout the stream of water. The distance $h$ vertically below the tap,where the cross-sectional area of the stream becomes $\frac{2}{3} A$,is (take $g = 10 \,m/s^2$): (in $\,m$)

The instrument fitted in the carburetor of an automobile to provide the correct mixture of air and fuel necessary for combustion works on which of the following principles?

The area of cross-section of a large tank is $0.5 \; m^{2}$. It has a narrow opening near the bottom having an area of cross-section $1 \; cm^{2}$. $A$ load of $25 \; kg$ is applied on the water at the top in the tank. Neglecting the speed of water in the tank,the velocity of the water coming out of the opening at the time when the height of water level in the tank is $40 \; cm$ above the bottom will be $\dots \; cm \; s^{-1}$. [Take $g = 10 \; m \; s^{-2}$]

Bernoulli's principle is based on the law of conservation of