Stress MCQ – Strength of Materials

1. A metal bar of length 200 m is inserted between 2 rigid supports and its temperature is increased by 30°C. If the coefficient of thermal expansion is 15 × 10-6 per °C and the Young’s modulus is 2 × 105 MPa, then the stress in the
bar is

  1. 90,000 MPa
  2. 60 MPa
  3. 6000 MPa
  4. 90 MPa
Answer
Answer. d

2. If all the dimensions of a prismatic bar increase in the proportion n : 1, the proportion with which the maximum stress produced in the bar by its own weight will change by

  1. 1 : n2
  2. 1 : n
  3. $\sqrt{n}$ : 1
  4. n : 1
Answer
Answer. d

3. A load of 100 kN suddenly acts on a bar of 100 cm2 area of cross-section and of length 300 mm. Maximum stress developed in the bar is

  1. 10 MPa
  2. 20 MPa
  3. 30 MPa
  4. 40 MPa
Answer
Answer. b

4. A rod 20 mm x 20 mm cross-section is carrying an axial tensile load 40 kN.what is the value of tensile stress developed in this rod?

  1. 100MPa
  2. 10 MPa
  3. 1 MPa
  4. 1000 MPa
Answer
Answer. a

5. A tube of aluminium of 40 mm external diameter and 20 mm internal diameter is snugly fitted on a solid steel rod of 20 mm diameter. The composite bar is subjected to an axial compressive force P. If the stress on steel bar is 70 N/mm2, the stress in the aluminium tube and corresponding value of P will be: (E for steel: 2 × 105 N/mm2 and E for aluminium: 7 × 104 N/mm2)

  1. 24.5 N/mm2, 45.08 kN
  2. 36.5 N/mm2, 60.10 kN
  3. 54.5 N/mm2, 73.10 kN
  4. 73.80 N/mm2, 92.60 kN
Answer
Answer. a

6. A Steel bar having cross-sectional area of 100π mm2 is subjected to a tensile force of 40 kN. Determine the tensile stress.

  1. 127.23 MPa
  2. 150 MPa
  3. 175.25 MPa
  4. 200.05 MPa
Answer
Answer. a

7. A square steel rod 20 mm × 20 mm in section is to carry an axial load of 100 kN. Calculate the stress.

  1. 1,50,000 kN/m2
  2. 2,50,000 kN/m2
  3. 4,50,000 kN/m2
  4. 3,50,000 kN/m2
Answer
Answer. b

8. The stress due to suddenly applied load is _________ times that of gradually applied load.

  1. 5
  2. 4
  3. 3
  4. 2
Answer
Answer. d

9. A steel rod of length ‘L’ and diameter ‘d’ fixed at both ends, is uniformly heated to a temperature rise of ΔT. The modulus of elasticity of material is ‘E’ and Thermal expansion coefficient is ‘α’. Thermal stress in rod is

  1. EαΔTL
  2. αΔT
  3. EαΔT
  4. zero
Answer
Answer. c

10. Type of stress that causes dilation is known as

  1. Thermal stress
  2. Shear stress
  3. Deviatoric stress
  4. Hydrostatic stress
Answer
Answer. d

11. A steel bar of 5 mm is heated from 15° to 40°C and it is free to expand. The bar will induce

  1. No stress
  2. Shear stress
  3. Tensile stress
  4. Compressive stress
Answer
Answer. a

12. The stress in a steel bar is given as 25,0000 kN/m2 and length of the bar is 50 m. Calculate the shortening of the bar if E = 2.14 × 108 N/mm2

  1. 0.160 mm
  2. 0.0584 mm
  3. 0.250 mm
  4. 0.305 mm
Answer
Answer. b

13. A steel bar of 500 mm length is under tensile stress of 100 N/mm2. If the modulus of elasticity is 2 × 1011 N/m2, then the total elongation of the bar will be

  1. 2.50 mm
  2. 0.25 mm
  3. 0.50 mm
  4. 5.00 mm
Answer
Answer. b

14. A concrete beam is post-tensioned by a cable carrying an initial stress of 1000 N/mm2, the slip of jacking end was observed to be 5 mm, modulus of steel is 210 kN/mm2 and span of beam is 30 m; what is % of loss of stress due to anchorage?

  1. 2.5%
  2. 3.5%
  3. 4.0%
  4. 1.5%
Answer
Answer. b

15. The rate of increase of stress is large in case of

  1. Unbonded beams
  2. Bonded beams
  3. Anchorage beams
  4. Tensioned beams
Answer
Answer. b

16. Subjected to axial load, the ductile material fails due to

  1. axial stress
  2. ductility
  3. axial strain
  4. shear stress
Answer
Answer. d

17. The unit of stress in S.I. unit is

  1. Kg/cm2
  2. Kg/m2
  3. N/m2
  4. N/cm2
Answer
Answer. c

18. A bar of cross-sectional area 2 cm2 and length 100 cm fixed to rigid supports at both ends at a temperature of 25°C. The bar is subjected to an increase in temperature of 30°C. If the coefficient of linear thermal expansion of the
material is 10 × 10-6 °C and Young’s modulus is 2 × 105 N/mm2, the stress in the bar is

  1. 10 N/mm2 comp
  2. 20 N/mm2 comp
  3. 50 N/mm2 tension
  4. 50 N/mm2 comp
Answer
Answer. a

19. The stress is ‘S’ when a body is subjected to a gradual load W on it. If the load is applied suddenly, the stress shall be

  1. S
  2. 2S
  3. 4S
  4. 1.5S
Answer
Answer. b

20. If a metal bar fixed at both ends is cooled by reducing the temperature by 30°C, the nature of the stress developed in the bar will be

  1. Shear
  2. Compressive
  3. Tensile
  4. None of the above
Answer
Answer. c
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