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Test: Viscosity - 2 - Mechanical Engineering MCQ


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10 Questions MCQ Test Fluid Mechanics for Mechanical Engineering - Test: Viscosity - 2

Test: Viscosity - 2 for Mechanical Engineering 2024 is part of Fluid Mechanics for Mechanical Engineering preparation. The Test: Viscosity - 2 questions and answers have been prepared according to the Mechanical Engineering exam syllabus.The Test: Viscosity - 2 MCQs are made for Mechanical Engineering 2024 Exam. Find important definitions, questions, notes, meanings, examples, exercises, MCQs and online tests for Test: Viscosity - 2 below.
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Test: Viscosity - 2 - Question 1

Two horizontal plates placed 250mm apart have an oil of viscosity 20 poises. Calculate the shear stress in oil if upper plate is moved with velocity of 1250mm/s.

Detailed Solution for Test: Viscosity - 2 - Question 1

Explanation: Shear Stress = Viscosity * Velocity Gradient
= 20/10* 1.25/0.25
= 10 N/m2.

Test: Viscosity - 2 - Question 2

The kinematic viscosity of oil of specific gravity .8 is .0005. This oil is used for lubrication of shafts diameter of .4 m and rotates at 190 rpm. Calculate the power lost in the bearing for a sleeve length of 90mm. The thickness of the oil film is 1.5mm.

Detailed Solution for Test: Viscosity - 2 - Question 2

Explanation: Power lost= torque * angular velocity
= force x radius x angular velocity
= shear stress x area x radius x angular velocity
Shear Stress = viscosity x velocity gradient
Power lost= 0.0005 x 0.8 x 1000 x 2 x 3.142 x 190/60 x 0.2 x 3.142 x 0.23 x 190/60
= 477.65 Watts.

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Test: Viscosity - 2 - Question 3

Find the kinematic viscosity of oil having density 1962 kg/m3. The force experienced for area of 20 m2 is 4.904 kN and velocity of gradient at that point is 0.2/s.

Detailed Solution for Test: Viscosity - 2 - Question 3

Explanation: kinematic viscosity = dynamic viscosity / density
= (shear stress*density)/velocity gradient
= (4904* 1962)/(20*0.2)
= 0.625.

Test: Viscosity - 2 - Question 4

The velocity distribution for fluid flow over a flat plate is given by u=2y-6y2 in which u is the velocity in metre per second at a distance of y metre above the plate. Determine the shear stress at y=0.15m.Take dynamic viscosity of fluid as 8.6 poise.

Detailed Solution for Test: Viscosity - 2 - Question 4

Explanation: for y = 0.15m, velocity gradient = 0.2
viscosity= shear stress/velocity gradient
shear stress = 0.86*0.2 = 0.172N/m2

Test: Viscosity - 2 - Question 5

In which types of fluids it is observed that momentum transfer dominates cohesive forces with increase in temperature and hence viscosity increases

Detailed Solution for Test: Viscosity - 2 - Question 5

Explanation: It is the characteristic property of gases which show increase in viscosity with increase in temperature.

Test: Viscosity - 2 - Question 6

What is the characteristic variation shown by the thixotropic fluids in their shear stress vs. rate of shear strain graph?

Detailed Solution for Test: Viscosity - 2 - Question 6

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.

Test: Viscosity - 2 - Question 7

What happens to viscosity in the case of incompressible fluids as temperature is increased?

Detailed Solution for Test: Viscosity - 2 - Question 7

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.

Test: Viscosity - 2 - Question 8

 If a fluid, which has a constant specific gravity, is taken to a planet where acceleration due to gravity is 3 times compared to its value on earth, what will happen to its kinematic viscosity.

Detailed Solution for Test: Viscosity - 2 - Question 8

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.

Test: Viscosity - 2 - Question 9

In liquids in order to measure the viscosity of fluid experimentally we consider the variation of shear stress with respect to what property?

Detailed Solution for Test: Viscosity - 2 - Question 9

Explanation: By definition, viscosity is shear stress per unit ‘rate of shear strain’.

Test: Viscosity - 2 - Question 10

For a compressible fluid the kinematic viscosity is affected by temperature and pressure variation.

Detailed Solution for Test: Viscosity - 2 - Question 10

Explanation: Viscosity shows variation for change in temperature and pressure for compressible fluids. Hence, kinematic viscosity is affected by temperature and pressure variation.

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