Engineering Questions with Answers - Multiple Choice Questions
Generalised Hooke’s Law
1 - Question
Hooke’s law states that within elastic limit, ______
a) stress is directly proportional to strain
b) stress is inversely proportional to strain
c) stress does not depend on strain
d) stress is equal to strain
View Answer
Answer: a
Explanation: In the simplest form, the Hooke’s law states that within the elastic limit, stress is directly proportional to strain.
∴ Stress ∝ Strain.
2 - Question
The generalised Hooke’s law equation connecting the strain to stress contains ___________ elastic constants.
a) 40
b) 36
c) 39
d) 38
View Answer
Answer: b
Explanation: The generalised Hooke’s law equation connecting the strain to stress contains 36 elastic constants. These elastic constants are independent of the stress components at a point.
3 - Question
An elastic body is said to be homogeneous if there are ______ elastic constants.
a) 36
b) 20
c) 26
d) 30
View Answer
Answer: a
Explanation: The generalised Hooke’s law equation connecting the strain to stress contains 36 elastic constants. When there are only 36 constants, then the elastic body is said to be homogeneous.
4 - Question
An elastic body is said to be isotropic if the elastic constants are ______
a) same only in y- direction
b) same only in x- direction
c) different in al direction
d) same in all direction
View Answer
Answer: d
Explanation: When the elastic constants are same in all the direction at a point in a soil body, then the soil body is said to be isotropic. By considering the homogeneity and the isotropy, the number of elastic constants reduces to only two.
5 - Question
The number of independent elastic constant is ______
a) 2
b) 5
c) 0
d) 6
View Answer
Answer: a
Explanation: Harr in 1966 showed that by a series of rotations of axes, the number of independent constants for a homogeneous and isotropic body is only two.
6 - Question
In the generalised Hook’s law equation, εX=C11σx+ C12 (σY+σZ), the constant C11 is __________
a) E
b) 1/E
c) 0
d) μ
View Answer
Answer: b
Explanation: Let us consider the case of uniaxial stress,
σY=σZ=0
∴ εX=C11σx
∴ C11= εX/σx=1/E.
7 - Question
In the generalised Hook’s law equation, εX=C11σx+ C12 (σY+σZ), the constant C12 is __________
a) E
b) 1/E
c) –μ/E
d) μ
View Answer
Answer: c
Explanation: Let us consider the case of uniaxial stress,
σY=σZ=0
∴ εX=C11σx
∴ C11= εX/σx=1/E and let, εY= εZ= C12σx
C12σx=E εX
∴ C12=(1/E)*( εY/ εX)
∴ C12=–μ/E.
8 - Question
The modulus of elasticity in MPa for very soft clay is __________
a) 2-15
b) 15-60
c) 50-81
d) 100-200
View Answer
Answer: a
Explanation: The modulus of elasticity in MPa for very soft clay is 2-15 MPa. For loess it is 15-60 MPa. For dense sand it is 50-81 MPa. And for sand and gravel it is 100-200 MPa.
9 - Question
The range of Poisson’s ratio μ for loess is _________
a) 0.1-0.3
b) 0.4-0.5
c) 0.3-0.35
d) 0.9-1
View Answer
Answer: a
Explanation: The range of Poisson’s ratio μ for loess is 0.1-0.3. The range of Poisson’s ratio μ for unsaturated clay is also 0.1-0.3. For saturated clay it is 0.4-0.5. For silt it is 0.3-0.35.