Mechanical properties of fluids practice · Easy

Surface tension of a liquid is numerically equal to

A barometer kept in an elevator reads $76 \mathrm{~cm}$ when it is at rest. If the elevator goes up with increasing speed, the reading will be

A block of volume $V$, floats in water with volume $\frac{V}{2}$ inside the water surface, now same block placed in another liquid, then floats with volume $\frac{V}{4}$ inside the liquid, then density of the liquid (in ${g} / {cm}^3$ ) is

The pressure on a swimmer, $10 {~m}$ below the surface of water is (let $g=10 {~m} / {s}^2$ and $1 {~atm}=10^5 {~N} / {m}^2$ )

Given below are two statements:

Statement-I: When a capillary tube is dipped into a liquid, the liquid neither rises nor falls in the capillary. The contact angle may be $0^{\circ}.$

Statement-II: The contact angle between a solid and a liquid is a property of the material of the solid and liquid as well.

In the light of above statement, choose the correct answer from the options given below.

Suppose that 64 raindrops combine into a single drop. Calculate the ratio of the total surface energy of the 64 drops to that of a single drop.

Where $\mathrm{T}=0.072 \mathrm{~N} / \mathrm{m}$

The reading of pressure meter attached with a closed pipe is $3.5 \times 10^4 \mathrm{~N} / \mathrm{m}^2$. On opening the valve of the pipe, the reading of the pressure meter is reduced to $3.0 \times 10^5$ $\mathrm{N} / \mathrm{m}^2$. Calculate the speed in $\mathrm{m} / \mathrm{s}$ of the water flowing in the pipe.

Water rises up to a height of 12 cm into a capillary tube when placed vertically. If it is now tilted through $45^\circ$ from the vertical, length of the water in the capillary tube is

A liquid rises in a vertical tube. The relation between the weight of the liquid in the tube, surface tension of the liquid $T$ and radius of the tube $r$ is given by (if the angle of contact is zero)

A uniform rod is 4 m long and weighs 10 kg. If it is supported on a knife edge at one metre from the end, what weight placed at that end keeps the rod horizontal?

Two droplets merge with each other and forms a large droplet. In this process

Two capillary tubes of same diameter are put vertically one each in two limbs whose relative densities are 0.8 and 0.6 and surface tension are 60 and 50 dyne/cm respectively. Ratio of heights of liquids in the two tubes is

Correct Bernoulli's equation is (symbols have their usual meaning) :

Two capillary tube of glass of radii 3 mm and 2 mm are placed vertically in water, ratio of height of water in the tubes is

Shape of liquid drop becomes spherical. It is due to

A cylinder of height 80 m is completely filled with water. The velocity of efflux of water (in m/s) through a small hole on the side wall of the cylinder near its bottom is $\left( {g = 10\,m/{s^2}} \right)$

A small liquid drop of radius $R$ is divided into 27 identical liquid drops. If the surface tension is $T$, then the work done in the process will be:

The meniscus of a liquid in a capillary tube is concave. If ${F_c}$ is the force of cohesion and ${F_A}$ is the force of adhesion between molecules of the liquid then

The excess pressure inside a soap bubble is thrice the excess pressure inside a second soap bubble. The ratio between the volume of the first and the second bubble is :

Small droplets of liquid are usually more spherical in shape than larger drops of the same liquid because

A narrow capillary tube when dipped in a beaker containing water the rise in 20 cm . If the area of cross-section of the bore is reduced to 1/4th value water will raise to a height of

Hair of shaving brush cling together when it is removed from water due to

The surface tension of a soap solution is $2 \times 10^{-2} \mathrm{Nm}^{-1}$. To blow a bubble of radius $1 \mathrm{~cm}$, the work done is

Assertion: Water drops take spherical shape when falling freely.
Reason: Water has minimum surface tension among all liquids.

Beyond the critical speed, the flow of fluids becomes

The excess pressure in a soap bubble is thrice that in other one. Then the ratio of their volume is

The additional force required to lift a flat circular disc of a radius 5 cm from the surface of water with surface tension $75\,\mathrm{dyne }c{m^{ - 1}}$ will be

Assertion: Sometimes insects can walk on water.
Reason: The gravitational force on insect is balanced by force due to surface tension.

A spherical soap bubble has a radius ${r}$. The surface tension of the soap film is $T$. The energy needed to double the diameter of the bubble at the same temperature is:

A large cylindrical vessel filled with a liquid up to a certain height is emptied by a horizontal capillary tube, filled to its base. Find the ratio of the time taken to empty the tank by one half, to the next one half?