Test: Viscosity - 2 - Mechanical Engineering MCQ

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

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.

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

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

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

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.

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.

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.

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

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