Viscosity MCQs : Here you will find MCQ Questions related to "Viscosity" in Fluid Mechanics. These Viscosity MCQ Questions Will help you to improve your Fluid Mechanics knowledge and will prepare you for various Examinations like Competitive Exams, Placements, Interviews and other Entrance Exmaniations
Water flows between two plates of which the upper one is stationary and the lower one is moving with a velocity V. What will be the velocity of the fluid in contact with the upper plate?
C. N ⁄ 2
Explanation: According to the No-Slip condition, the relative velocity between the plate and the fluid in contact with it must be zero. Thus, the velocity of the fluid in contact with the upper plate is 0 and that with the lower plate is V.
The viscous force the relative motion between the adjacent layers of a fluid in motion.Which one of the flowing fits best in the sentence?
B. never affects
D. may effect under certain conditions
Explanation: Viscosity is the internal friction of a fluid in motion. It is the property by the virtue of which the relative motion between two adjacent fluid layers is opposed.
The viscosity of a fluid in motion is 1 Poise. What will be it’s viscosity (in Poise) when the fluid is at rest?
Explanation: Viscosity is the property of a fluid and is constant for a given fluid under given conditions, irrespective of the fact whether the fluid is at rest or in motion.
Which of the following correctly states how the viscosities of a liquid and a gas will change with temperature?
A. Viscosity increases with the increase in temperature of a liquid and decreases with the increase in temperature of a gas
B. Viscosity increases with the increase in temperature of a liquid and increases with the increase in temperature of a gas
C. Viscosity decreases with the increase in temperature of a liquid and decreases with the increase in temperature of a gas
D. Viscosity decreases with the increase in temperature of a liquid and increases with the increase in temperature of a gas
Explanation: Viscosity of a liquid is due to the cohesion between it’s molecules. With the increase in temperature of a liquid, cohesion increases, leading to the rise in viscosity. Viscosity of a gas is due to the momentum transfer between it’s molecules. With the increase in the temperature of a liquid, molecular motion increases, leading to the fall in viscosity.
The kinematic viscosity of a fluid is 0.1 Stokes. What will be the value is (m^2)/s?
Explanation: 1Stokes = 1cm^2/s = (10^-4)m^2/s Therefore, 0.1Stokes = (10^-1)cm^2/s = (10^-5)m^2/s.
Two horizontal plates placed 250mm have an oil of viscosity 20 poises. Calculate the shear stress in oil if upper plate is moved with velocity of 1250mm/s.
A. 20 N/m^2
B. 2 N/m^2
C. 10 N/m^2
D. 1 N/m^2
Explanation: Shear Stress = Viscosity * Velocity Gradient = 20/10* 1.25/0.25 = 10 N/m^2.
In which types of fluids it is observed that momentum transfer dominates cohesive forces with increase in temperature and hence viscosity increases
D. All of the above
Explanation: It is the characteristic property of gases which show increase in viscosity with increase in temperature.
What is the characteristic variation shown by the thixotropic fluids in their shear stress vs. rate of shear strain graph?
A. shear stress increases with increase in rate of shear strain
B. shear stress decreases with increase in rate of shear strain
C. shear stress shows variation only after a definite shear stress is reached
D. shear stress has decreasing constant and then variation relationship with rate of shear strain
Explanation: Thixotropic fluid show a Non-Newtonian variation for shear stress vs. rate of shear strain graph after a characteristic limiting value of shear stress is reached.
Kinematic viscosity depends on density and dynamic viscosity
C. Can be true or false
D. Can not say
Explanation: Kinematic viscosity depends on density and dynamic viscosity. Both, density and dynamic viscosity, are independent of acceleration due to gravity. Therefore, kinematic viscosity is independent of acceleration due to gravity.
What happens to viscosity in the case of incompressible fluids as temperature is increased
A. It remains constant
B. It increases
C. It decreases
D. None of the above
Explanation: In case of incompressible fluids, cohesive forces govern the viscosity. As temperature increases the cohesive forces between fluid molecules decreases due to increase in molecular agitation. Hence, as a result, viscosity decreases.