An airplane of a total wing area of \(120\) ${\mathrm{m}}^2$ is in a level flight at some height. If the pressure difference between the upper and lower surface is \(2.5\) kPa, then the mass of the airplane is: (Take \(g=10\) ${\mathrm{ms}}^{-2}$)

1.	\(2\times10^3\) kg	2.	\(3\times10^4\) kg
3.	\(5\times10^4\) kg	4.	\(7\times10^4\) kg

An air bubble of radius r in water is at a certain depth below the water surface. If P is the pressure inside the bubble, then the depth below the water surface is: [\(P_{0}\) = Atmospheric pressure, \(\rho\) = Density of water, T = surface tension of water]

1.  \(\frac{P   -   P_{0}}{ρg}   -   \frac{4 T}{rρg}\)

2.  \(\frac{P   +   P_{0}}{ρg}   +   \frac{2 T}{rρg}\)

3.  \(\frac{P   -   P_{0}}{ρg}   -   \frac{2 T}{rρg}\)

4.  \(\frac{P   -   P_{0}}{ρg}   +   \frac{2 T}{2 rρg}\)

A block weighs 5 N in air and 4.5 N in a liquid of specific gravity 0.5. Its weight in water will be:

1. 3.5 N

2. 4.0 N

3. 2.5 N

4. 3.0 N

A liquid is poured into three vessels of the same base area and equal heights as shown in the figure, then:
                                  

A liquid is filled in a container as shown in the figure. The force exerted by the liquid on the base of the container must be:
                                 

The surface tension of a liquid is \(5\) N m^-1. If a film is held on a ring of area \(0.02\) ${\mathrm{m}}^2$, then its total surface energy is:
1. \(3\times\) ${10}^{-2}$ J
2. \(2\times\) ${10}^{-1}$ J
3. \(3\times\) ${10}^{-3}$J
4. ${10}^{-1}$ J

A liquid filled in a container has plane meniscus. If $\mathrm{\theta }$ is the angle of contact, then:
1. $\mathrm{\theta }$ = \(0^\circ\)
2. $\mathrm{\theta }$ = \(90^\circ\)
3. $\mathrm{\theta }$ < \(90^\circ\)
4. $\mathrm{\theta }$ = \(180^\circ\)

The relative velocity of two adjacent layers of a liquid is 6 cm/s and the perpendicular distance between layers is 0.1 mm. The velocity gradient for liquid (in per second) is:

A large open tank with a square hole of side \(0.1\) cm in the wall at a depth of \(0.2\) m from the top is completely filled with a liquid. The rate of flow of liquid (in ${\mathrm{cm}}^3$/s) through the hole will be: 

The property of surface tension of the liquid is due to: