Fluid Mechanics

81.An ideal plastic substance indicates no deformation, when stressed upto yield stress, but behaves like a Newtonian fluid beyond yield stress. Which of the following is an ideal plastic?

  1. Sewage sludge
  2. Rubber latex
  3. Blood
  4. Sugar solution
Correct answer: (A)
Sewage sludge

82.An isentropic process is the one, in which

  1. pv = constant
  2. pvr= constant
  3. pvr = constant, and process is reversible
  4. None of these
Correct answer: (C)

pvr = constant, and process is reversible

83.Applicability of Bernoulli's equation is limited to a/an _________ fluid, that does not exchange shaft work with the surroundings.

  1. Incompressible
  2. Non-viscous
  3. Both (A) and (B)
  4. Neither (A) nor (B)
Correct answer: (C)
Both (A) and (B)

84.Applying a pressure drop across a capillary results in a volumetric flow rate 'Q' under laminar flow conditions. The flow rate for the same pressure drop, in a capillary of the same length but half the radius is

  1. Q/2
  2. Q/4
  3. Q/8
  4. Q/16
Correct answer: (D)
Q/16

85.As per Newton's law of viscosity, the shear stress for a given rate of angular deformation of fluid is proportional to (where, μ = fluid viscosity)

  1. 1/μ
  2. μ
  3. μ2
  4. 1/μ2
Correct answer: (B)
μ

86.As the velocity V and thus the Reynolds number of a flow past a sphere increases from very low value, the drag force for Re << 1

  1. Increases linearly with V
  2. Decreases linearly with V
  3. Decreases as v2
  4. None of these
Correct answer: (A)
Increases linearly with V

87.Assuming flow to be laminar, if the diameter of the pipe is halved, then the pressure drop will

  1. Increase
  2. Decrease
  3. Remain same
  4. Be quadrupled
Correct answer: (A)
Increase

88.At a constant speed of the centrifugal pump, it‟s _________ the impeller diameter.

  1. Capacity varies directly with
  2. Head varies as the square of
  3. Horsepower varies as the cube of
  4. All (A), (B) and (C)
Correct answer: (D)
All (A), (B) and (C)

89.At high Reynolds number

  1. Inertial forces control and viscous forces are unimportant
  2. Viscous forces predominate
  3. Inertial forces are unimportant and viscous forces control
  4. None of these
Correct answer: (A)
Inertial forces control and viscous forces are unimportant

90.At low Reynolds number

  1. Viscous forces are unimportant
  2. Viscous forces control
  3. Viscous forces control and inertial forces are unimportant
  4. Gravity forces control
Correct answer: (C)
Viscous forces control and inertial forces are unimportant
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