Mechanical properties of fluids practice · Medium

Water from a tap emerges vertically downwards with initial velocity $4 \mathrm{~ms}^{-1}$. The cross-sectional area of the tap is $A$. The flow is steady and pressure is constant throughout the stream of water. The distance $h$ vertically below the tap, where the cross-sectional area of the stream becomes $(2 / 3) A$, is (Take, $g=10 \mathrm{~m} \mathrm{~s}^{-2}$ )

A: Kerosene Oil spreads out over water surface
R: Surface tension is a surface phenomenon

The viscous force on a lead shot travelling down with velocity V in a liquid column is F. If the same lead shot travelling down with velocity 3V in an other vertical liquid column is opposed by viscous force 2F, the ratio of the coefficients of viscosities of the liquids is

A good lubricant should have

The excess pressure in a bubble of radius R of a gas in a liquid of surface tension S is

Water rises to a height of $9 \mathrm{~cm}$ in a certain capillary tube. If in the same tube, level of ${Hg}$ is depressed by $3 \mathrm{~cm}$, compare the surface tension of water and mercury. Specific gravity of ${Hg}$ is $13.6,$ the angle of contact for water is zero and that for ${Hg}$ is $135^{\circ}$.

An aeroplane of mass $3 \times {10^4}$ kg and total wing area of $120{\mathrm{m}^2}$ is in a level flight at some height. The difference in pressure between the upper and lower surface of its wings in kilo pascals is $\left( {\mathrm{g} = 10\mathrm{m}{\mathrm{s}^{ - 2}}} \right)$

An aluminium sphere is dipped into water. Which of the following is true?

Water is flowing through two horizontal pipes of different diameters which are connected together. The diameters of the two pipes are $3 \mathrm{~cm}$ and $6 \mathrm{~cm}$, respectively. If the speed of water in the narrower tube is $4 \mathrm{~ms}^{-1}$, then the speed of water in the wider tube is

When a cylindrical tube is dipped vertically into a liquid the angle of contact is ${140^\mathrm{o}}$, when the tube is dipped with an in inclination of ${40^ \circ }$ the angle of contact is

A closed vessel is half-filled with water. There is a hole near the top of the vessel and air is pumped out from this hole

Express standard atmospheric pressure in bars.

A: A large soap bubble expands while a small bubble shrinks, when they are connected to each other by a capillary tube
R: The excess pressure inside bubble (or drop) is inversely proportional to the radius

The amount of work done in increasing size of soap film $6 \mathrm{~cm} \times 4 \mathrm{~cm}$ to $12 \mathrm{~cm} \times 8 \mathrm{~cm}$ is: (surface tension $30 \mathrm{~dyne}/ \mathrm{cm}$)

If two soap bubble of different radii are connected by a tube

A block of ice in which a piece of stone is embedded is floating on water contained in a beaker. When all the ice melts, the level of water in the beaker

The coefficient of viscosity of a liquid does not depend upon:

In a turbulent flow, the velocity of the liquid in contact with the walls of the tube is

The length of a needle floating on water is $2.5 \mathrm{~cm}$. How much minimum force, in addition to the weight of the needle, will be needed to lift the needle above the surface of water? Surface tension of water $=7.2 \times 10^{-4} \mathrm{~Ncm}^{-1}$.

At what speed will the velocity head of stream of water be $40 \mathrm{~cm}$?

Express standard atmospheric pressure in torr.

Bernouli's equation is valid for

A jeweller claims that he sells ornaments made of pure gold that has the relative density of $19.3.$ He sells a necklace weighing $25.250 \mathrm{~g f}$ to a person. The clever customer weighs the necklace when immersed in pure water and finds that it weighs $23.075 \mathrm{~g f}$ in water. Is the ornament made of pure gold?

A soap bubble has radius $'r'$. What will be the value of work done if its radius increases to three times of initial value without changing temperature (surface tension of soap solution is $'T'$)

Statement-A: Mosquitos are killed (which are present in water) when kerosene is sprayed on water surface in tanks or ponds.
Statement-B: Kerosene is very harmful for mosquitoes.

The potential energy of molecule on the surface of a liquid compared to one inside the liquid is

A drop of water of volume $V$ is pressed between the two glass plates so as to spread to an area $A$. If $S$ is the surface tension, then normal force required to separate the glass plates is

$\mathbf{A}$ : An iron needle placed carefully on the surface of water may float, whereas a solid ball of same material will always sink

$\mathbf{R}$ : The buoyancy on an object depends both on the material and shape of object.

Scent sprayer is based on

Which of the following statement(s) is/are correct?

I. An ice ball is floating in water. Some stone pieces are embedded inside the ice. When ice will melt, level of water will fall.

II. In floating condition, stone pieces will displace more liquid compared to the condition when they sink.