4. Strength of Materials 100 Exam-Pattern MCQs with Detailed Answers

byᒪEᗩᖇᑎ ᑕIᐯIᒪ EᗩᔕY -
0

 

Strength of Materials

100 Exam-Pattern MCQs with Detailed Answers

🔹 Stress, Strain & Elastic Constants

1. A bar of area 500 mm² carries a load of 100 kN. The stress in the bar is

A) 100 MPa
B) 150 MPa
C) 200 MPa
D) 250 MPa

Ans: C
Detail:

σ=PA=100×103500=200 N/mm2=200 MPa\sigma=\frac{P}{A}=\frac{100\times10^3}{500}=200\text{ N/mm}^2=200\text{ MPa}

2. A bar elongates by 1 mm over a length of 2 m. Strain is

A) 0.002
B) 0.0005
C) 0.001
D) 0.005

Ans: B
Detail:

ε=ΔLL=12000=0.0005\varepsilon=\frac{\Delta L}{L}=\frac{1}{2000}=0.0005

3. Young’s modulus is a measure of

A) Strength
B) Stiffness
C) Toughness
D) Hardness

Ans: B
Detail: Higher E → less deformation for same load.

4. If Poisson’s ratio of a material is 0.5, the material is

A) Brittle
B) Perfectly plastic
C) Incompressible
D) Perfectly elastic

Ans: C
Detail: μ = 0.5 → volume remains constant.

5. Elastic limit is the point

A) Of fracture
B) Where permanent deformation begins
C) Of maximum stress
D) Of necking

Ans: B
Detail: Beyond elastic limit, deformation is permanent.

🔹 Axial Load & Thermal Stress

6. A bar 2 m long, area 400 mm², E = 200 GPa carries load 80 kN. Elongation is

A) 1 mm
B) 2 mm
C) 3 mm
D) 4 mm

Ans: A
Detail:

δ=PLAE=80×103×2000400×200×103=1 mm\delta=\frac{PL}{AE}=\frac{80\times10^3\times2000}{400\times200\times10^3}=1\text{ mm}

7. Thermal stress develops in a bar when

A) It is free to expand
B) Expansion is restrained
C) Temperature falls
D) Length is large

Ans: B
Detail:

σ=EαΔT\sigma=E\alpha\Delta T

8. A steel bar is fixed at both ends and heated. Stress developed will be

A) Tensile
B) Compressive
C) Shear
D) Zero

Ans: B
Detail: Expansion prevented → compressive stress.

9. In bars connected in series, which is same?

A) Stress
B) Strain
C) Force
D) Area

Ans: C
Detail: Same axial force passes through all bars.

10. In bars connected in parallel, which is same?

A) Stress
B) Strain
C) Force
D) Area

Ans: B
Detail: Ends move together → equal strain.

🔹 Torsion of Shafts

11. Torsion equation is

A) M/I = σ/y
B) T/J = τ/R = Gθ/L
C) P/A
D) σ = Eε

Ans: B
Detail: Fundamental relation for circular shafts.

12. Maximum shear stress in a solid shaft occurs at

A) Centre
B) Outer surface
C) Mid-radius
D) Neutral axis

Ans: B
Detail: τ ∝ r.

13. A hollow shaft is preferred over solid because

A) Cheaper
B) Less weight
C) Higher strength-to-weight ratio
D) Less length

Ans: C
Detail: More material away from centre → higher J.

14. Power transmitted by a shaft is

A) NT
B) 2πNT/60
C) T/N
D) N/T

Ans: B
Detail: Standard power equation.

15. A shaft transmitting constant power at double speed will have torque

A) Same
B) Double
C) Half
D) Four times

Ans: C
Detail:

P=2πNT60⇒T∝1NP=\frac{2\pi NT}{60}\Rightarrow T\propto\frac{1}{N}

🔹 Bending of Beams

16. Neutral axis of a homogeneous beam passes through

A) Top fibre
B) Bottom fibre
C) Centroid
D) Shear centre

Ans: C
Detail: Due to symmetric stress distribution.

17. Bending stress equation is

A) σ = M/I
B) σ = My/I
C) σ = Iy/M
D) σ = M/y

Ans: B
Detail: Flexure formula.

18. Maximum bending stress occurs at

A) Neutral axis
B) Farthest fibre
C) Centroid
D) Support

Ans: B
Detail: y is maximum there.

19. Section modulus is defined as

A) I/ymax
B) I×ymax
C) A/y
D) y/I

Ans: A
Detail: Measures bending strength.

20. In a cantilever beam, maximum BM occurs at

A) Free end
B) Fixed end
C) Mid-span
D) Quarter span

Ans: B
Detail: Maximum moment at fixed support.

🔹 Shear Stress in Beams

21. Average shear stress in beam is

A) V/A
B) VQ/It
C) M/I
D) T/J

Ans: A
Detail: Simple average value.

22. Maximum shear stress in rectangular beam is

A) τavg
B) 1.5τavg
C) 2τavg
D) 0.5τavg

Ans: B
Detail: τmax = 1.5 V/A.

23. Shear stress is zero at

A) Neutral axis
B) Outer surface
C) Centre
D) Supports

Ans: B
Detail: In bending theory.

24. In I-section beam, maximum shear stress occurs at

A) Flange
B) Web at NA
C) Top fibre
D) Bottom fibre

Ans: B
Detail: Web carries most shear.

25. Shear stress distribution in rectangular beam is

A) Uniform
B) Linear
C) Parabolic
D) Triangular

Ans: C
Detail: Max at NA, zero at surfaces.

🔹 Columns & Buckling

26. Column failure mainly occurs due to

A) Crushing
B) Buckling
C) Shear
D) Torsion

Ans: B
Detail: Stability failure.

27. Slenderness ratio is

A) L/A
B) L/k
C) A/L
D) I/A

Ans: B
Detail: k = radius of gyration.

28. Euler’s formula is valid for

A) Short columns
B) Intermediate columns
C) Long columns
D) All columns

Ans: C
Detail: Elastic buckling only.

29. Critical load is

A) Yield load
B) Buckling load
C) Breaking load
D) Crushing load

Ans: B
Detail: Load at instability.

30. Column with both ends fixed has effective length

A) L
B) 2L
C) L/2
D) √2L

Ans: C
Detail: Strongest end condition.

🔹 Strain Energy & Impact

31. Strain energy in a bar under axial load is

A) PL/AE
B) P²L/2AE
C) P²L/AE
D) PL/2AE

Ans: B
Detail:

U=Pδ2U=\frac{P\delta}{2}

32. For suddenly applied load, maximum stress is

A) Same as static
B) Half of static
C) Double of static
D) Zero

Ans: C
Detail: Dynamic factor = 2.

33. Impact loading causes

A) Lower stress
B) Same stress
C) Higher stress
D) Zero stress

Ans: C
Detail: Due to kinetic energy.

34. Proof resilience is

A) Total strain energy
B) Elastic strain energy per unit volume
C) Plastic energy
D) Impact energy

Ans: B
Detail: Energy stored up to elastic limit.

35. Toughness equals area under

A) Elastic region
B) Plastic region
C) Entire stress-strain curve
D) Yield region

Ans: C
Detail: Energy to fracture.

🔹 Fatigue & Stress Concentration

36. Fatigue failure occurs due to

A) Static loading
B) Repeated loading
C) Impact loading
D) Thermal loading

Ans: B
Detail: Cyclic stresses cause cracks.

37. Endurance limit is

A) Maximum stress
B) Safe cyclic stress
C) Yield stress
D) Ultimate stress

Ans: B
Detail: Infinite life below this stress.

38. Stress concentration occurs due to

A) Uniform section
B) Sudden change in section
C) Smooth surface
D) Long length

Ans: B
Detail: Local rise in stress.

39. Stress concentration factor is

A) Max stress / Nominal stress
B) Nominal / Max
C) Stress / strain
D) Load / area

Ans: A
Detail: Indicates severity.

40. Fillets are provided to

A) Increase stress
B) Reduce stress concentration
C) Reduce weight
D) Increase length

Ans: B
Detail: Smooth transition reduces stress peak.

🔹 Combined Stress & Failure Theories

41. Principal stresses occur on planes where

A) Normal stress is zero
B) Shear stress is zero
C) Bending stress is zero
D) Load is zero

Ans: B
Detail: Definition of principal plane.

42. Maximum shear stress in biaxial stress is

A) (σ₁ + σ₂)/2
B) (σ₁ − σ₂)/2
C) σ₁
D) σ₂

Ans: B
Detail: From Mohr’s circle.

43. Tresca theory is called

A) Maximum principal stress theory
B) Maximum shear stress theory
C) Maximum strain theory
D) Distortion energy theory

Ans: B
Detail: Used for ductile materials.

44. Von Mises theory is based on

A) Maximum shear stress
B) Maximum principal stress
C) Distortion energy
D) Total strain energy

Ans: C
Detail: Most accurate for ductile metals.

45. Rankine theory is used for

A) Ductile materials
B) Brittle materials
C) Rubber
D) Plastics

Ans: B
Detail: Based on max normal stress.

🔹 Deflection of Beams

46. Deflection of beam varies with

A) L²
B) L³
C) L⁴
D) L⁵

Ans: C
Detail:

δ∝L4EI\delta \propto \frac{L^4}{EI}

47. Maximum deflection in simply supported beam with central load occurs at

A) Quarter span
B) Mid span
C) Support
D) One-third span

Ans: B
Detail: Symmetry of loading.

48. Unit load method is used to find

A) Stress
B) Bending moment
C) Deflection
D) Torque

Ans: C
Detail: Based on virtual work.

49. Conjugate beam method finds

A) BM
B) SF
C) Slope & deflection
D) Stress

Ans: C
Detail: Structural analysis technique.

50. Beam becomes stiffer when

A) Length increases
B) Depth increases
C) Load increases
D) Area decreases

Ans: B
Detail: I ∝ depth³.

🔹 Miscellaneous (51–100 condensed but exam-level)

  1. Hardness means resistance to → Scratching

  2. Ductility is measured by → % elongation

  3. Cast iron is best in → Compression

  4. Steel is generally → Ductile

  5. Proof stress is used when → Yield point is not clear

  6. Neutral axis shifts when → Section is unsymmetrical

  7. Shear centre is point where → Load causes no twisting

  8. A beam under transverse load has → Shear + bending stress

  9. Weakest column end condition → Fixed–free

  10. Beam of uniform strength has → Constant stress

  11. A long column fails by → Buckling

  12. Strain has → No unit

  13. Working stress = → Ultimate stress / FOS

  14. Toughness is → Total energy to fracture

  15. Resilience is → Elastic energy

  16. Bending stress varies → Linearly with distance from NA

  17. Shear stress max in rectangular beam at → Neutral axis

  18. A hollow shaft is stronger because → Higher polar moment

  19. Power in shaft = → 2πNT/60

  20. Euler load ∝ → 1/L²

  21. Column buckles in plane of → Minimum I

  22. Rankine formula combines → Crushing + buckling

  23. Strain energy method finds → Deflection

  24. Impact factor is highest for → Falling load

  25. Fatigue is dangerous because → No warning before failure

  26. Stress concentration is highest at → Sharp corner

  27. Tresca is conservative because → Gives lower safe stress

  28. Von Mises is best for → Ductile materials

  29. Rankine is best for → Brittle materials

  30. Shear stress in shaft is → Zero at centre

  31. Beam under pure bending has → Only BM

  32. Condition for max BM → SF = 0

  33. Slenderness ratio = → L/k

  34. Radius of gyration = → √(I/A)

  35. Strain energy in spring = → ½kδ²

  36. Perfectly plastic material has → Constant stress after yield

  37. A beam of equal strength has → Constant Z

  38. Shaft safest in torsion is → Hollow

  39. Most dangerous load is → Impact load

  40. Best theory for combined loading in ductile → Von Mises

  41. Stress concentration factor is theoretical because → Assumes elasticity

  42. Fatigue strength decreases due to → Corrosion

  43. Plane stress exists in → Thin plates

  44. Plane strain exists in → Long dams

  45. A composite beam’s NA shifts toward → Higher E material

  46. Product of inertia zero for → Principal axes

  47. A deep beam fails by → Shear

  48. Column design for brittle → Buckling stress

  49. Deflection reduces when → EI increases

  50. Safest design theory for shafts → Von Mises theory

Tags:

Post a Comment

Previous Post Next Post