The correct statement about the variation of viscosity of fluids with an increase in temperature is:

1. viscosity of gases decreases.
2. viscosity of both liquids and gases increases.
3. viscosity of liquids increases.
4. viscosity of liquids decreases.
Subtopic:  Viscosity |
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Water on the surface of a river \(10\) m deep is observed to be flowing at \(5\) m/s. The shearing stress between horizontal layers of the river is:
(\(\eta=10^{-3}\) SI units)
1. \(10^{-3}\) N/m2
2. \(0.8 \times 10^{-3}\) N/m2
3. \(0.5 \times 10^{-3}\) N/m2
4. \(1\) N/m2
Subtopic:  Viscosity |
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The velocity of the upper layer of water in a river is \(36\) kmh–1. Shearing stress between horizontal layers of water is \(10^{-3}\) Nm–2. Depth of the river is:
(coefficient of viscosity of water is \(10^{-2}\) Pa-s)
1. \(100\) m
2. \(200\) m
3. \(300\) m
4. \(400\) m
Subtopic:  Viscosity |
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A metal block of area \(0.10~\text{m}^{2}\) is connected to a \(0.010~\text{kg}\) mass via a string that passes over an ideal pulley (considered massless and frictionless), as in the figure below. A liquid film with a thickness of \(0.30~\text{mm}\) is placed between the block and the table. When released the block moves to the right with a constant speed of \(0.085~\text{m/s}.\) The coefficient of viscosity of the liquid is:

          
1. \(4.45 \times 10^{-2}~\text{Pa-s}\)
2. \(4.45 \times 10^{-3}~\text{Pa-s}\)
3. \(3.45 \times 10^{-2}~\text{Pa-s}\)
4. \(3.45 \times 10^{-3}~\text{Pa-s}\)

Subtopic:  Viscosity |
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A thin rectangular metal plate \(10~\text{cm}\times5\text{ cm }\)is lying on the layer of glycerine of thickness \(1\) mm and coefficient of viscosity \(0.8\text{ Pa-s.}\) What is the horizontal force needed to move the plate with a speed of \(15\text{ cm s}^{–1}\) on the liquid?
1. \(0.2\) N
2. \(0.4\) N
3. \(0.6\) N
4. \(1.4\) N
Subtopic:  Viscosity |
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With an increase in temperature, the viscosity of:
(a) gases decrease. (b) liquids increase.
(c) gases increase. (d) liquids decrease.

Which of the following options is/are correct?
1. (b), (c) 2. (a), (d)
3. (c), (d) 4. (a), (b)
Subtopic:  Viscosity |
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A solid sphere, of radius \(R,\) acquires a terminal velocity \(v_1\) when falling (due to gravity) through a viscous fluid having a coefficient of viscosity \(\eta.\) The sphere is broken into \(27\) identical solid spheres. If each of these spheres acquires a terminal velocity, \(v_2\), when falling through the same fluid, the ratio \(\left(\dfrac{v_1}{v_2}\right) \) equals:
1. \(\dfrac{1}{9}\)
2. \(\dfrac{1}{27}\)
3. \(9\)
4. \(27\)

Subtopic:  Viscosity |
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Two raindrops reach the earth with different terminal velocities having a ratio \(9:4.\) Then the ratio of their volumes is:
1. \(3:2\)
2. \(4:9\)
3. \(9:4\)
4. \(27:8\)
Subtopic:  Viscosity |
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A spherical ball is dropped in a long column of a highly viscous liquid. The curve in the graph shown, which represents the speed of the ball (\(v\)) as a function of time (\(t\)) is:
           
1. \(D\)
2. \(A\)
3. \(B\)
4. \(C\)
Subtopic:  Viscosity |
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Two small spherical metal balls, having equal masses, are made from materials of densities \(\rho_1\) and \(\rho_2\) such that \(\rho_1=8\rho_2\) and having radii of \(1\) mm and \(2\) mm, respectively. They are made to fall vertically (from rest) in a viscous medium whose coefficient of viscosity equals \(\eta\) and whose density is \(0.1\rho_2\). The ratio of their terminal velocities would be:

1. \(\dfrac{79}{72}\) 2. \(\dfrac{19}{36}\)
3. \(\dfrac{39}{72}\) 4. \(\dfrac{79}{36}\)
Subtopic:  Viscosity |
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