The pressure of water in a water pipe when the tap is closed and opened is $3.5 \times 10^5 \, N/m^2$ and $3 \times 10^5 \, N/m^2$ respectively. With the tap open,the velocity of water flowing is ........... $m/s$. (Take density of water $\rho = 10^3 \, kg/m^3$)

$A$ 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

Rank in order, from highest to lowest, the liquid heights $h_a$ to $h_d$. The air flow is from left to right. The liquid columns are not drawn to scale.

What is the Magnus effect?

$A$ bottle has a thin nozzle on top. It is filled with water,held horizontally at a height of $1 \,m$ and squeezed slowly by hands,so that the water jet coming out of the nozzle hits the ground at a distance of $2 \,m$. If the area over which the hands squeeze it is $10 \,cm^{2}$,the force applied by hand is close to .......... $N$ (take $g=10 \,m/s^{2}$ and density of water $=1000 \,kg/m^{3}$).

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