# Quiz: Civil Engineering 24 Nov 2020

Quiz: Civil Engineering
Exam: RSMSSB-JEn
Topic: Strength of Materials

Each question carries 1 mark
Negative marking: 1/3 mark
Time: 10 Minutes

Q1. Maximum strain energy theory for the failure of a material at the elastic limit is known as
(a) Guest’s or Tresca’s theory
(b) St. Venant’s theory
(c) Rankine’s theory
(d) Haigh’s theory

Q2. The ability of a material to absorb energy till the breaking or rupture takes place is known as
(a) Hardness
(b) Toughness
(c) Brittleness
(d) Softness

Q3. If a load of 40 KN is applied in a compressive manner on a rod whose cross section is 10 mm ×20mm, then what will be the compressive stress on the rod in MPa?
(a) 0.2
(b) 2
(c) 20
(d) 200

Q4. A material has identical properties in all directions is said to be
(a) Homogeneous
(b) Isotropic
(c) Anisotropic
(d) Orthotropic

Q5. The Poisson’s ratio for concrete is approximately
(a) 0.15
(b) 0.3
(c) 0.05
(d) 0.5

Q6. In an experiment it found that the bulk modulus of a material is equal to its shear modulus. This Poisson’s ratio is.
(a) 0.125
(b) 0.250
(c) 0.375
(d) 0.500

Q7. Angle of twist of a circular shaft under the action of a torsional moment T is given by
(a) GJ/TL
(b) TL/GJ
(c) TJ/GL
(d) TG/JL

Q8. If a ductile material is subjected to a unidirectional tensile force, then to avoid shear failure, the material should have its shear strength at least equal to
(a) its tensile strength
(b) Half the tensile strength
(c) Its compressive strength
(d) Twice the tensile strength

Q9. During a tensile test on a specimen of 1 cm² cross-section, maximum load observed was 8 tonnes and area of cross-section at neck was 0.5 cm³. Ultimate tensile strength of specimen is
(a) 4 tonnes/cm²
(b) 8 tonnes/cm²
(c) 16 tonnes/cm²
(d) 22 tonnes/cm²

Q10. Ratio of moment of inertia of a circle and that of a square having same area about their centroidal axis is–
(a) 3/π
(b) 3/2π
(c) 4/π
(d) 5/9π

SOLUTIONS

S1. Ans.(d)
Sol. → Maximum principal strain theory (St. Venant’s theory)
→ Maximum principal stress theory (Rankine’s theory)
→ Maximum strain energy theory (Bectami-Haigh’s Theory)
→ Maximum shear stress theory (Huber Hencky von-mises theory)

S2. Ans.(b)
Sol. Toughness is the ability of material to absorb energy till the breaking or rupture takes place. It is equal to total area under load deflection curve up to fracture.

S3. Ans.(d)
Sol. Given,
P=40 kN=40×10^3 N
A=10×20 mm^2
σ= ?
σ=P/A
=(40×10^3)/(10×20)
▭(σ=200 MPa)

S4. Ans.(b)
Sol. Isotropic → A material is said to be isotropic when it has same properties in all direction.
Anisotropic → A material is said to be anisotropic when it has different properties in all direction.
Homogenous → Same property at each cross-section.
Orthotropic → Different property in three mutually perpendicular direction.

S5. Ans.(a)

Sol.

 Type of material Poission ratio Cork 0 Glass 0.01 to 0.05 Concrete 0.1 to 0.2 Steel 0.288 Aluminium 0.33 Bronze 0.35

S6. Ans.(a)
Sol. Given bulk modulus (K) = Shear modulus (G)
Now,
Poisson’s ratio (μ)=(3K-2G)/(6K+2G)=(3-2)/(6+2)=1/8=0.125

S7. Ans.(b)
Sol. form the Torsion equation →
T/J=Gθ/L
▭(θ=TL/GJ)
Where θ = angle of twist
T= Applied twisting moment
L= Length of the shaft
G= Modulus of rigidity
J= Polar moment of inertia

S8. Ans.(d)
Sol. If ductile material is subjected to a unidirectional tensile force, then to avoid shear failure material should have its shear strength is twice the tensile strength.

S9. Ans.(b)
Sol. We know that
Ultimate tensile Strength=(Maximum Load)/(Original area of cross-section)
=8/1
Ultimate tensile strength =8 Tonnes\/cm^2

S10. Ans.(a)
Sol. I_circle=π/64 d^4 I_square=a^4/12
Given that area is same
A_square=A_circule
a^2=π/4 d^2
a=√π/2 d
I_circle/I_square =(π/64 d^4)/(d^4/12)
I_circle/I_square =(π/64 d^4)/(1/12 π^2/16×d^4 )
I_circle/I_square =3/π

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