Engineering Questions with Answers - Multiple Choice Questions
Fluid Mechanics MCQ – Types of Fluids
1 - Question
The relation between shear stress Z and velocity gradient
of a fluid is given by
where A and n are constants. If n = 1, what type of fluid will it be?
a) Newtonian fluid
b) Non-Newtonian fluid
c) Pseudoplastic
d) Bingham plastic
View Answer
Answer: a
Explanation: When n = 1, the relation reduces to Newton’s law of viscosity: z = A *
where A will represent the viscosity of the fluid. The fluid following this relation will be a Newtonian fluid.
2 - Question
The relation between shear stress Z and velocity gradient
of a fluid is given by
where A and n are constants. If n > 1, what type of fluid will it be?
a) Newtonian fluid
b) Dilatant
c) Pseudoplastic
d) Bingham plastic
View Answer
Answer: b
Explanation: When n ≠ 1, the relation will be treated as Power law for Non-Newtonian fluids:
For n > 1, the rate of change of the shear stress increases with the increase in the value of velocity gradient. Such fluids are called Dilatants.
3 - Question
The relation between shear stress Z and velocity gradient
of a fluid is given by
here A and n are constants. If n < 1, what type of fluid will it be?
a) Newtonian fluid
b) Dilatant
c) Pseudoplastic
d) Bingham plastic
View Answer
Answer: c
Explanation: When n ≠ 1, the relation will be treated as Power law for Non-Newtonian fluids:
For n < 1, the rate of change of the shear stress decreases with the increase in the value of velocity gradient. Such fluids are called Pseudoplastics.
4 - Question
The relation between shear stress Z and velocity gradient 
f a fluid is given by
+ B where A, n and B are constants. Which of the following conditions will hold for a Bingham plastic?
a) A = 0;B ≠ 0; n ≠ 1
b) A ≠ 0;B = 0; n ≠ 1
c) A = 0;B = 0; n = 1
d) A ≠ 0;B ≠ 0; n = 1
View Answer
Answer: d
Explanation: For Bingham Plastics, shear stress will not remain constant after an yield value of stress. Thus, A ≠ 0;B ≠ 0. After the yield value, the relation between the shear stress and velocity gradient will become linear. hus, n = 1.
5 - Question
The relation between shear stress Z and velocity gradient
of a fluid is given by
+ B where A, n and B are constants. Which of the following conditions will hold for a Rheopectic?
a) A = 0;B ≠ 0; n > 1
b) A ≠ 0;B = 0; n < 1
c) A = 0;B = 0; n < 1
d) A ≠ 0;B ≠ 0; n > 1
View Answer
Answer: d
Explanation: For Rheopectics, shear stress will not remain constant after an yield value of stress. Thus, A ≠ 0; B ≠ 0. After the yield value, the rate of change of the shear stress increases with the increase in the value of velocity gradient. Thus, n > 1.
6 - Question
The relation between shear stress Z and velocity gradientf a fluid is given by + B where A, n and B are constants. Which of the following conditions will hold for a Thixotropic fluid?
a) A = 0;B ≠ 0; n > 1
b) A ≠ 0;B = 0; n > 1
c) A = 0;B = 0; n < 1
d) A ≠ 0;B ≠ 0; n < 1
View Answer
Answer: d
Explanation: For Thixotropics, shear stress will not remain constant after an yield value of stress. Thus, A ≠ 0;B ≠ 0. After the yield value, the rate of change of the shear stress decreases with the increase in the value of velocity gradient. Thus, n < 1.
7 - Question
The graph shows relation between shear stress Z and velocity gradientof a fluid is given where A and n are constants. The graphs are drawn for three values of n. Which one will be the correct relationship between n1, n2 and n3?
a) n1 > n2 > n3
b) n1 < n2 < n3
c) n1 > n3 > n2
d) n1 < n3 < n2
View Answer
Answer: b
Explanation: The graph corresponding to n = n1 represents Pseudoplastics, for which the rate of change of the shear stress decreases with the increase in the value of velocity gradient. The graph corresponding to n = n2 represents Newtonian fluids, for which shear stress changes linearly with the change in velocity gradient. The graph corresponding to n = n3 represents Dilatents, for which the rate of change of the shear stress increases with the increase in the value of velocity gradient.
8 - Question
Which of the following is a shear-thinnning fluid?
a) Bingham plastic
b) Rheopectic
c) Dilatant
d) Pseudoplastic
View Answer
Answer: d
Explanation: Shear-thinning fluids are those which gets strained easily at high values of shear stresses. The relation between shear stress Z and velocity gradient of a shear-thinning fluid is given by
where A and n are constants and n < 1. This relation is followed by Pseudoplastics.
9 - Question
Which of the following is a shear-thickening fluid?
a) Bingham plastic
b) Thixotropic
c) Dilatant
d) Pseudoplastic
View Answer
Answer: c
Explanation: Shear-thickening fluids are those for which it gets harger to strain it at high values of shear stresses. The relation between shear stress Z and velocity gradient of a shear-thickening fluid is given by where A and n are constants and n > 1. This relation is followed by Dilatants.
10 - Question
For what value of flow behaviour index, does the consistency index has a dimension independent of time?
a) 0
b) 1
c) 2
d) 3
View Answer
Answer: c
Explanation: The relation between shear stress Z and velocity gradient of a fluid is given by
where A is the flow consistency index and n is the flow behaviour index.
Thus [A] will be independent of time when n = 2.
11 - Question
What will be the dimension of the flow consistency index for a fluid with a flow behaviour index of 3?
a) [M L-2 T].
b) [M L-2 T-1].
c) [M L-1 T-2].
d) [M L-1 T].
View Answer
Answer: d
Explanation: The relation between shear stress Z and velocity gradient of a fluid is given by
where A is the flow consistency index and n is the flow behaviour index. Putting n = 3,
12 - Question
What will be the dimension of the flow consistency index for a fluid with a flow behaviour index of -1?
a) N/m2 s2
b) N/m2 s
c) N/ms
d) N/ms2
View Answer
Answer: b
Explanation: The relation between shear stress Z and velocity gradient of a fluid is given by
where A is the flow consistency index and n is the flow behaviour index. If n = -1, A = Z * Unit of Z is N/m2 and is s-1. Thus, the unit of A will be N/m2 s.