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 $(g = 10 \, m/s^2)$.

State Bernoulli's principle in words.

An $L$-shaped tube with a small orifice is held in a water stream as shown in the figure. The upper end of the tube is $10.6 \ cm$ above the surface of the water. What will be the height (in $cm$) of the jet of water coming from the orifice? The velocity of the water stream is $2.45 \ m/s$. (Take $g = 9.8 \ m/s^2$)

In this figure,an ideal liquid flows through a tube of uniform cross-section. The liquid has velocities $v_A$ and $v_B$,and pressures $P_A$ and $P_B$ at points $A$ and $B$ respectively.

$A$ liquid enters at point $A_{1}$ with a speed of $3.5 \ m/s$ and leaves at point $A_{2}$. Find the height attained by the liquid above point $A_{2}$ (in $cm$). (in $.25$)

In a test experiment on a model aeroplane in a wind tunnel,the flow speeds on the upper and lower surfaces of the wing are $70 \; m s^{-1}$ and $63 \; m s^{-1}$ respectively. What is the lift on the wing if its area is $2.5 \; m^{2}$? Take the density of air to be $1.3 \; kg m^{-3}$.