# The viscous force acting between two layers of a liquid is given by $$\frac FA=-\eta\frac{dv}{dz}$$. This F/A may be called 1. pressure 2. longitudinal stress 3. tangential stress 4. volume stress

Subtopic:  Viscosity |
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A raindrop falls near the surface of the earth with almost uniform velocity because

1. its weight is negligible

2. the force of surface tension balances its weight

3. the force of viscosity of air balances its weight

4. the drops are charged and atmospheric electric field balances its weight

Subtopic:  Viscosity |
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A piece of wood is taken deep inside a long column of water and released. It will move up

1. with a constant upward acceleration

2. with a decreasing upward acceleration

3. with a deceleration

4. with a uniform velocity

Subtopic:  Viscosity |
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A solid sphere falls with a terminal velocity of 20 m s–1 in air. If it is allowed to fall in vacuum,

1. terminal velocity will be 20 m s–1

2. terminal velocity will be less than 20 m s–1

3. terminal velocity will be more than 20 m s–1

4. there will be no terminal velocity

Subtopic:  Viscosity |
64%
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A spherical ball is dropped in a long column of a viscous liquid. The speed of the ball ($$v$$) as a function of time ($$t$$) may be best represented by the graph:

1. $$\mathrm{D}$$
2. $$\mathrm{B}$$
3. $$\mathrm{A}$$
4. $$\mathrm{C}$$

Subtopic:  Viscosity |
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The properties of a surface are different from those of the bulk liquid because the surface molecules

 (a) are smaller than other molecules (b) acquire charge due to collision from air molecules (c) find different types of molecules in their range of influence (d) feel a net force in one direction

Choose the correct option:
 1 (a) and (b) 2 (b) and (c) 3 (c) and (d) 4 All of these
Subtopic:  Properties of Fluids |
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The rise of a liquid in a capillary tube depends on

(a) the material

(b) the length

(d) the inner radius of the tube

Choose the correct option:

1. (a) and (b)

2. (a), (b) and (c)

3. (a), (b) and (d)

4. All of these

Subtopic:  Capillary Rise |
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The contact angle between a solid and a liquid is a property of

(a) the material of the solid

(b) the material of the liquid

(c) the shape of the solid

(d) the mass of the solid

Choose the correct option:

1. (a) and (b)

2. (b) and (c)

3. (c) and (d)

4. All of these

Subtopic:  Surface Tension |
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A liquid is contained in a vertical tube of semicircular cross-section (figure). The contact angle is zero. The forces of surface tension on the curved part and on the flat part are in ratio:

1. $$1:1$$
2. $$1:2$$
3. $$\pi:2$$
4. $$2: \pi$$

Subtopic:  Surface Tension |
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When a capillary tube is dipped into a liquid, the liquid neither rises nor falls in the capillary.

 a. the surface tension of the liquid must be zero. b. the contact angle must be $$90^\circ.$$ c. the surface tension may be zero. d. the contact angle may be $$90^\circ.$$

Choose the correct option:

 1 (a) and (b) 2 (b) and (c) 3 (c) and (d) 4 all of these

Subtopic:  Capillary Rise |
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