Question 1 : If the surface of a liquid is plane, then the angle of contact of the liquid with the walls of container is

Question 2 : Materials for rain-proof coats and tents owe their water-proof properties due to

Question 3 : Calculate the energy spent in spraying a drop of mercury of radius $R$ into $n$ dropletsall of same size. Given the surface tension of mercury is  $T .$

Question 4 : Let air be at rest at the front edge of a wing and air passing over the surface of wing at a fast speed v. If density of air is $\rho$, the highest value for v in streamline flow when atmospheric pressure is $P_{atmosphere}$ is:<br/>

Question 5 : A spherical ball of diameter $1$cm and density $5\times 10^3$kg $m^{-3}$ is dropped gently in a large tank containing viscous liquid of density $3\times 10^3$kg $m^{-3}$ and coefficient of viscosity $0.1$Ns $m^{-2}$. The distance, the ball moves in $1$s after attaining terminal velocity is $(g=10ms^{-2})$.

Question 6 : How much work will be done in enlarging the surface area of a soap bubble by $1.0 cm^2 $?&#160;<br/>

Question 7 : When a solid ball of volume V is falling through a viscous liquid, a viscous force F acts on it. If another ball of volume 2V of the same material is falling through the same liquid then the viscous force experienced by it will be (when both fall with terminal velocities).

Question 8 : Each of 27 identical spherical drops of a conducting liquid is charged upto a potential of Vo. They coal ease to form a bigger drop. What is the potential on the surface of this bigger drop.

Question 9 : A spherical ball of iron of radius $2\ \text{mm}$ is falling through a column of glycerine. If densities of glycerine and iron are respectively $1.3\times 10^3\ \text{kg/m}^3$ and $8\times 10^3\ \text{kg/m}^3$. $\eta\ {for \ glycerine} = 0.83\ \text{Nm}^{-2}\ \text{sec},$ then the terminal velocity is:

Question 10 : A vertical tank, open at the top, is filled with a liquid and rests on a smooth horizontal surface. A small hole is opened at the centre of one side of the tank. The area of cross-section of the tank is $N$ times the area of the hole, where $N$ is a large number. Neglect mass of the tank itself. The inital acceleration of the tank is <br>

Question 12 : The reading of a pressure meter attached with a closed water pipe is 3.5 x 10$^{5}$ N m$^{-2}$. On opening the valve of the pipe, the reading of pressure meter is reduced to 3 x 10$^{5}$ N m$^{-2}$. Calculate the speed of water flowing in the pipe.

Question 13 : Consider a soap film on a rectangular frame of wire of area $4 \times 4 cm^2$. If the area of the soap film is increased to $4 \times 5cm^2$, the work done in the process will be (The surface tension of the soap film is $3 \times 10^{-2} N/m$)

Question 14 : An air bubble of radius 5 $\times $ 10$^{-4}$m rises in a liquid&#160;of viscosity 0.1 Pas (g$=10ms^{-2}$) and density&#160;900kgm$^{-3}$. The terminal velocity of the bubble is:

Question 15 : Two hail stones with radii in the ratio of $1:2$ fall from a great height through the atmosphere. Then the ratio of their momenta after they have attained terminal velocity is

Question 16 : A cylindrical vessel is filled with water up to height $H$. A hole is bored in the wall at a depth $h$ from the free surface of water. For maximum range, $h$ is equal to :-<br>

Question 18 : The excess pressure inside one soap bubble is three times that inside a second soap bubble. The ratio of the volumes of the two bubbles is

Question 19 : Due to air a falling body faces a resistive force proportional to square of velocity $v$, consequently its effective downward acceleration is reduced and is given by $a = g - kv^{2}$ where $k = 0.002m^{-1}$. The terminal velocity of the falling body is (in m/s)<br/>

Question 20 : A wind - powered generator converts wind energy&#160;into electrical energy. Assume that the generator&#160;converts a fixed fraction of the wind energy&#160;intercepted by its blades into electrical energy. For wind speed $V$, the electrical power output will&#160;be proportional to