Water is filled to a height $H$ behind a dam of width $w$. The resultant force on the dam is ..............

Mercury is filled in a tube of radius $2 \,cm$ up to a height of $30 \,cm$. The force exerted by mercury on the bottom of the tube is . . . . . . $N$.
(Given: atmospheric pressure $P_0 = 10^5 \,N/m^2$,density of mercury $\rho = 1.36 \times 10^4 \,kg/m^3$,$g = 10 \,m/s^2$,$\pi = \frac{22}{7}$)

Water flowing through a pipe of area of cross-section $2 \times 10^{-3} \,m^2$ hits a vertical wall horizontally with a velocity of $12 \,m \,s^{-1}$. If the water does not rebound after hitting the wall, then the force acting on the wall due to water is (in $\,N$)

$A$ tube of length $L = 1 \ m$ is filled completely with an ideal liquid of mass $M_{total} = 2M$,and closed at both ends. The tube is rotated uniformly in a horizontal plane about one of its ends. If the force exerted by the liquid at the other end is $F$,then the angular velocity of the tube is $\sqrt{\frac{F}{\alpha M}}$ in $SI$ units. The value of $\alpha$ is . . . . . . .

$A$ pressure-pump has a horizontal tube of cross-sectional area $10 \, cm^{2}$ for the outflow of water at a speed of $20 \, m/s$. The force exerted on the vertical wall just in front of the tube,which stops the water horizontally flowing out of the tube,is $... N$ [Given: density of water $= 1000 \, kg/m^{3}$].

$A$ jet of water with a cross-section of $6 \ cm^2$ strikes a wall at an angle of $60^{\circ}$ to the normal and rebounds elastically from the wall without losing energy. If the velocity of the water in the jet is $12 \ m/s$,the force acting on the wall is ....... $N$.