Structures · MCQ practice Stress and Strain MCQs – Part 3
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Part 3 of 3 Question 31 Easy
For the principle of superposition to be valid, materials should behave in which manner?
A linear-elastic B non-linear elastic C non-linear inelastic D linear inelastic
Answer: A. linear-elastic
Superposition (adding effects of separate loads) needs linear-elastic behaviour (and small deflections).
Question 32 Medium
Which of the following statements is false?
A Mild steel has 2 yield points B Mild steel shows strain hardening C Mild steel is a ductile material D None of these
Answer: D. None of these
All three statements are true for mild steel, so none is false: (d).
Question 33 Medium
If the Young's modulus of a material is twice its modulus of rigidity, its Poisson's ratio is:
A −1 B −0.5 C 0.5 D None of these
Answer: D. None of these
E = 2G(1 + μ) with E = 2G gives μ = 0, which is not listed: (d). (The revised key marked (a); see the note.)
Question 34 Medium
Which of the following statements is true?
A The sum of normal stresses is constant B The sum of normal stresses is variable C The sum of normal stresses depends on the plane D None of these
Answer: A. The sum of normal stresses is constant
At a point, the sum of normal stresses on any two mutually perpendicular planes is constant (σx + σy = σ1 + σ2).
Question 35 Easy
Poisson's ratio is defined as the:
A ratio of lateral strain to linear strain B ratio of linear strain to lateral strain C ratio of lateral stress to linear stress D ratio of linear stress to lateral stress
Answer: A. ratio of lateral strain to linear strain
μ = lateral strain ÷ linear (longitudinal) strain.
Question 36 Medium
A compound bar has a steel bar (3500 mm²) and a brass bar (3000 mm²) of equal length carrying a compressive load of 100,000 N. If Es = 0.2 MN/mm² and Eb = 0.1 MN/mm², the stresses developed are:
A σb = 10 N/mm², σs = 20 N/mm² B σb = 8 N/mm², σs = 16 N/mm² C σb = 6 N/mm², σs = 12 N/mm² D σb = 5 N/mm², σs = 10 N/mm²
Answer: A. σb = 10 N/mm², σs = 20 N/mm²
Equal strain: σs/σb = Es/Eb = 2. Then 3500(2σb) + 3000σb = 100,000 → σb = 10, σs = 20 N/mm².
Question 37 Medium
A material obeying Hooke's law carries a direct stress σ₀. At its elastic limit, which statement is true?
A Strain is equal to σ₀/E B Maximum shear stress = σ₀/2 C Strain energy = (σ₀²/2E) × volume D All options are correct
Answer: D. All options are correct
All three are standard results for uniaxial stress within the elastic range.
Question 38 Easy
What is the limit of Poisson's ratio?
A 0.1 B 0.2 C 0.3 D None of these
Answer: D. None of these
For isotropic engineering materials Poisson's ratio ranges from 0 to 0.5; the upper limit 0.5 is not listed, so (d).
Question 39 Easy
Among the following, which is least elastic?
A Iron B Copper C Both copper and silver D Rubber
Answer: D. Rubber
In engineering terms elasticity is measured by the modulus of elasticity; rubber has by far the lowest, so it is the least elastic.
Question 40 Medium
Two bars of different materials have the same size and carry the same tensile force. If their unit elongations are in the ratio 4 : 7, the ratio of their moduli of elasticity is: (1) 4 : 7 (2) 4 : 10 (3) 16 : 49
A 1 only B 2 only C 3 only D None of these
Answer: D. None of these
Same stress, so E ∝ 1/strain: E₁ : E₂ = 7 : 4 — not listed, so (d).
Question 41 Medium
If a composite bar of steel and copper is heated, the copper bar will be under:
A Tension B Shear C Torsion D None of these
Answer: D. None of these
Copper expands more than steel, so it is held back and goes into compression — not listed, so (d).
Question 42 Medium
A steel rod of area 25 mm² connects two parallel walls 5 m apart. The nuts were tightened when the rod was at 100 °C. If α = 0.000012 /°C and E = 0.2 MN/mm², the tensile stress developed when the temperature falls to 50 °C is:
A 80 N/mm² B 100 N/mm² C 120 N/mm² D 150 N/mm²
Answer: C. 120 N/mm²
σ = EαΔT = 2 × 10⁵ × 12 × 10⁻⁶ × 50 = 120 N/mm² (tension).
Question 43 Easy
Which of the following is a dimensionless quantity?
A Strain B Modulus of elasticity C Shear force D Stress
Answer: A. Strain
Strain = change in length ÷ original length — a ratio of lengths, so it has no dimensions.
Question 44 Easy
A load of 1960 N is raised at the end of a steel wire. The minimum diameter of the wire so that the stress does not exceed 100 N/mm² is:
A 4.0 mm B 4.5 mm C 5.0 mm D 5.5 mm
Answer: C. 5.0 mm
A = 1960/100 = 19.6 mm²; d = √(4A/π) ≈ 5.0 mm.
Question 45 Easy
A bar of length L and cross-sectional area A carries a gradually applied tensile load W. The strain energy stored in the bar is:
A WL/2AE B WL/AE C W²L/AE D W²L/2AE
Answer: D. W²L/2AE
U = ½Wδ = ½W(WL/AE) = W²L/2AE.
Part 3 of 3