Viscosity Multiple Choice Questions and Answers

1. The relative motion between the adjacent layers of a fluid in motion is called viscous force. Which of the flowing suits the best in the sentence?

1. Effects at some conditions
2. Never affects
3. Opposes
4. Facilitates

Answer: Opposes

2. A body just floats in sea water but sinks in river water because:

1. Sea water has lesser density than river water.
2. Sea water has greater density than river water.
3. Sea water exerts less upthrust on the body than river water./li>
4. River water is more contaminated than sea water.

Answer: Sea water has greater density than river water.

3. What is the unit of coefficient of viscosity?

1. Ns/m2
2. Nm/s
3. Ns/m
4. Nm/s2

Answer: Ns/m2

4. What is the effect of temperature increase on viscosity of liquids and gases?

1. Increases for both liquids and gases
2. Increases for liquids and decreases for gases
3. Increases for gases and decreases for liquids
4. Decreases for both liquids and gases

Answer: Increases for gases and decreases for liquids

5. On which these factors does air/fluid resistance force, acting on a spherical body, not depend?

1. Radius of body
2. Velocity of body
3. Coefficient of viscosity
4. Density of body

Answer: Density of body

6. What will be the terminal velocity of a rain drop of radius (r) 1mm and mass (M) 0.001g falling through air. The coefficient of viscosity of air (η) is 1.8 X 10-5Ns/m2? Neglect buoyant force.

1. 20 m/s
2. 29.47 m/s
3. 35.8 m/s
4. 40 m/s

Answer: 29.47 m/s

7. What do we call the maximum velocity of a fluid in a tube for which the flow remains streamlined?

1. Hyper velocity
2. critical velocity
3. Stream velocity
4. Laminar velocity

Answer: critical velocity

8. Which is the following is the correct definition of solubility?

1. The rate at which a solute dissolves into a solvent
2. The ability of a solid particle to disperse throughout a liquid continuous phase
3. The rate at which the immiscible liquid droplets disperse within a second in the liquid phase
4. The ability of a solute to dissolve into a solvent

Answer: The ability of a solute to dissolve into a solvent

9. Viscosity is said to be internal friction between fluid layers. What type of force is it?

1. Electromagnetic
2. Gravitational
3. Weak Nuclear forces
4. Strong Nuclear forces

Answer: Electromagnetic

10. A block of mass 2kg is going down an incline over a fluid having some viscosity. The block moves with a constant speed of 5m/s. Assuming that the temperature of fluid remains constant, find the coefficient of viscosity of the fluid. Angle of incline is 30° & block is a cube of side 1m. Also given that the thickness of fluid is 1cm.

1. 2 poise
2. 0.2 poise
3. 0.17 Ns/m2
4. 1.7 poise

Answer: 0.2 poise

11. In a closed pipe of radius R, fluid (having some viscosity) is flowing laminarly. Which point along a cross section will have maximum speed?

1. Centre
2. Near the wall of pipe
3. R/2 from centre
4. All points will have same speed

Answer: Centre

12. Which of these fluids has the highest viscosity?

1. Water
2. Honey
3. Blood
4. Air

Answer: Honey

13. Which of these ratios gives the value of viscosity of fluid?

1. Ratio of the shearing stress to the weight of the fluid
2. Ratio of the shearing stress to the density of the fluid
3. Ratio of the velocity gradient and shearing stress
4. The ratio of the shearing stress to the velocity gradient

Answer: The ratio of the shearing stress to the velocity gradient

14. What is the relation between the viscosities of blood and water?

1. Both are equal.
2. Water is more viscous than blood.
3. Blood is more viscous than water.
4. They cannot be compared.

Answer: Blood is more viscous than water.

15. Which of the following represents viscosity?

1. Potential energy stored in fluid
2. Resistance to fluid motion
3. Roughness of the surface
4. The pressure difference between the two fluids

Answer: Resistance to fluid motion

16. Which among the following statement is the definition of a pseudoplastic liquid?

1. It is a liquid that becomes less viscous over time when constant shear stress is applied
2. As the rate of shear increases, it becomes less viscous
3. When constant shear stress is applied the liquid becomes more viscous over time
4. A liquid which becomes more viscous as the rate of shear increases

Answer: It is a liquid that becomes less viscous as the rate of shear increases

17. What is the SI unit of viscosity?

1. Candela
2. Poiseiulle
3. Newton/m
4. No units

Answer: Poiseiulle

18. The friction in a flowing fluid is called ________.

1. Density
2. Surface tension
3. Viscosity
4. More than one of the above

Answer: Viscosity

19. What happens to the viscosity of liquid with the increase in temperature

1. It increases
2. It decreases
3. It may increase or decrease
4. No change

Answer: It decreases

20. Whether an object will float or sink in a liquid, depends on

1. the mass of the object only
2. the mass of the object and density of liquid only
3. the difference in the densities of the object and liquid
4. the mass and shape of the object only

Answer: the difference in the densities of the object and liquid

21. 1 poise = _________ Ns/m2. Fill in the blanks.

1. 0.01
2. 0.1
3. 1
4. 10

Answer: 0.1

22. The viscosity of liquid

1. Increases with increase in temperature
2. Decreases with increase in temperature
3. Decreases with decrease in temperature
4. Remains constant regardless of any change in the temperature

Answer: Decreases with increase in temperature

23. Which of the following represents Kinematic viscosity?

1. Viscosity/temperature
2. Viscosity/area
3. Viscosity/density
4. Viscosity/mass

Answer: Viscosity/density