Engineering Questions with Answers - Multiple Choice Questions
Fluid Mechanics MCQ – Compressibility and Bulk Modulus
1 - Question
Which one of the following is the correct relation between compressibility β and Bulk Modulus k
a) β = k
b) β = 1/k
c) β = 2k
d) β = k/2
View Answer
Answer: b
Explanation: Compressibility β of a liquid is deβned as the ratio of volumetric strain to the compressive stress while Bulk Modulus is the ratio of compressive stress to volumetric strain. Hence, β = 1/k is the correct relation.
2 - Question
Which one of the following is true about Bulk Modulus of elasticity?
a) it is the ratio of compressive stress to volumetric strain
b) it is the ratio of compressive stress to linear strain
c) it is the ratio of tensile stress to volumetric strain
d) it is the ratio of tensile stress to linear strain
View Answer
Answer: a
Explanation: Bulk Modulus k is related to the compression of a liquid and the decrease in volume per unit volume. It is the ratio of compressive stress to the volumetric strain.
3 - Question
The value of the Bulk Modulus of elasticity for an incompressible fluid is
a) zero
b) unity
c) infinity
d) very low
View Answer
Answer: c
Explanation: k = 1/β, where k= Bulk Modulus of elasticity and β= compressibility. For an incompressible fluid, β=0, thus the value of k will tend to infinity.
4 - Question
Three fluids 1, 2 and 3 have Bulk Moduli of k1, k2 and k3 respectively. If k1 > k2 > k3, which liquid will have the highest compressibility?
a) liquid 1
b) liquid 2
c) liquid 3
d) they’ll have equal compressibilities
View Answer
Answer: c
Explanation: k = 1=β, where k= Bulk Modulus of elasticity and β= compressibility. If k1 > k2 > k3, then β1 < β2 < β3. Thus, liquid 3 will have the highest compressibility.
5 - Question
Bulk Modulus, Pressure, Force, Stress – Which one of these won’t have the same unit as the others?
a) Bulk Modulus
b) Pressure
c) Force
d) Stress
View Answer
Answer: c
Explanation: The SI unit of Bulk Modulus, Pressure and Stress is N/m2 but the unit of Force is N.
6 - Question
Which of the following is the dimension of Bulk Modulus?
a) [M1L-1T-1].
b) [M1L-1T-2].
c) [M1L1T-2].
d) [M1L1T-1].
View Answer
Answer: b
Explanation:
7 - Question
Which one of the following is the unit of compressibility?
a) m=N
b) m2=N
c) m3=N
d) it is unitless
View Answer
Answer: b
Explanation: k = 1/β, where k= Bulk Modulus of elasticity and β= compressibility.
Thus the unit of Bulk modulus is N/m2 and the unit of compressibility becomes m2/N.
8 - Question
Which of the following is the dimension of compressibility?
a) [M1L1T-2].
b) [M1L1T-1].
c) [M-1L1T-2].
d) [M-1L1T2].
View Answer
Answer: d
Explanation: k = 1/β, where k = Bulk Modulus of elasticity and β= compressibility.
and [β] = [1/k] = [M-1L1T2].