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The meniscus of mercury in a capillary glass tube, is

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Important Questions on Mechanical Properties of Matter

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A large number of water drops, each of radius r, combine to have a drop of radius R. If the surface tension is T and mechanical equivalent of heat is J, the rise in heat energy per unit volume will be:
EASY
Two separate soap bubbles of radii 3×10-3 m and 2×10-3 m respectively, formed of same liquid (surface tension 65×10-2 N m-1) come together to form a double bubble. The radius of interface of double bubble is
EASY
Pressure inside two soap bubbles are 1.01 and 1.02 atmosphere, respectively. The ratio of their volumes is :
EASY
If a soap bubble expands, the pressure inside the bubble
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A soap bubble, blown by a mechanical pump at the mouth of a tube increases in volume with time at a constant rate. The graph that correctly depicts the time dependence of pressure inside the bubble is given by:
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A soap bubble of radius 3 cm is formed inside another soap bubble of radius, 6 cm. The radius of an equivalent soap bubble that has the same excess pressure as inside the smaller bubble with respect to the atmospheric pressure is____cm.
EASY
A soap bubble having radius of 1 mm is blown from a detergent solution having a surface tension of 2.5×10-2N m-1. The pressure inside the bubble equals at a point Z0 below the free surface of water in a container. Taking g=10 m s-2, density of water =103 kg m-3, the value of Z0 is
EASY
The radius R of the soap bubble is doubled under isothermal condition. If T be the surface tension of the soap bubble, the work done in doing so is given by
HARD

If two glass plates have water between them and are separated by very small distance (see figure), it is very difficult to pull them apart. It is because the water in between forms cylindrical surface on the side that gives rise to lower pressure in the water in comparison to atmosphere. If the radius of the cylindrical surface is R and surface tension of water is T then the pressure in water between the plates is lower by:

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HARD
A small soap bubble of radius 4cm is trapped inside another bubble of radius 6cm without any contact. Let P2 be the pressure inside the inner bubble and P0, the pressure outside the outer bubble. Radius of another bubble with pressure difference P2-P0 between its inside and outside would be:
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A spherical soap bubble of radius 3 cm is formed inside another spherical soap bubble of radius 6 cm. If the internal pressure of the smaller bubble of radius 3 cm in the above system is equal to the internal pressure of the another single soap bubble of radius r cm. The value of r is _____
EASY
A liquid will not wet the surface of a solid, if the angle of contact is
HARD
A bubble has surface tension S. The ideal gas inside the bubble has ratio of specific heats γ=53. The bubble is exposed to the atmosphere and it always retains its spherical shape. When the atmospheric pressure is Pa1, the radius of the bubble is found to be r1 and the temperature of the enclosed gas is T1. When the atmospheric pressure is Pa2, the radius of the bubble and the temperature of the enclosed gas are r2 and T2, respectively. Which of the following statement(s) is(are) correct?
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A boy formed a bubble and a liquid drop form the same soapy water. The pressure difference between inside and outside of the soap bubble is measured to be 100 N/m2. If the radius of the droplet is half of the radius of the bubble, then the pressure difference between the inside and outside of the droplet is
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An air bubble of radius 1 mm is at a depth of 8 cm below the free surface of a liquid column. If the surface tension and density of the liquid is 0.1 N m-1 and 2000 kg m-3 respectively, by what amount is the pressure inside the bubble greater than the atmospheric pressure?
(Take g=10 m s-2)
EASY
Water rises to a height 'h' in capillary tube. If the length of capillary tube above the surface of water is made less than 'h', then:
HARD
A uniform capillary tube of inner radius r is dipped vertically into a beaker filled with water. The water rises to a height h in the capillary tube above the water surface in the beaker. The surface tension of water is σ . The angle of contact between water and the wall of the capillary tube is θ . Ignore the mass of water in the meniscus. Which of the following statements is (are) true?
EASY
A glass capillary tube is of the shape of a truncated cone with an apex angle α so that its two ends have cross-sections of different radii. When dipped in water vertically, the water rises in it to a height h, where the radius of its cross-section is b. If the surface tension of water is S, its density is ρ, and its contact angle with glass is θ, then the value of h will be (g is the acceleration due to gravity)

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EASY

Given below are two statements: One is labelled as Assertion (A) and the other is labelled as Reason (R).

Assertion (A): Clothes containing oil or grease stains cannot be cleaned by water wash.

Reason (R): Because the angle of contact between the oil/grease and water is obtuse. In light of the above statements, choose the correct answer from the option given below.

EASY
Identify the incorrect statement about 'angle of contact':
(a) Angle of contact depends upon the inclination of the solid surface to the liquid surface.
(b) If the angle of contact of a liquid and a solid surface is less than 90°, then the liquid spreads on the surface of the solid.
(c) Angle of contact increases with increase in temperature of liquid.
(d) The value of angle of contact for pure water and glass is zero.