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# Materials Science MCQ’s – Stress and Strain

1 - Question

Up to which point on the stress-strain curve is Hooke’s law valid?

a) Elastic limit

b) Yield point

c) Proportionality limit

d) Fracture point

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Answer: cExplanation: The proportionality limit is the point up till which the strain of an elastic body is proportional to the stress applied on it. While elastic point is the point up till which the elastic properties last. After fracture point the body breaks.

2 - Question

What is the unit for stress?

a) N/m2

b) Nm2

c) N/m

d) Nm

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Answer: aExplanation: Stress is basically forced upon the unit area. The dimension for force is N and the dimension of area is m2. Therefore, the unit for stress is the dimension of force divided by that of area which is N/mm2.

3 - Question

Strain is a dimensionless quantity.

a) True

b) False

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Answer: aExplanation: Strain is defined as the deformation produced on a body due to stress divided by a length of the body. Deformation due to longitudinal strength will have the same unit as that of length of the body therefore, strain is a dimensionless quantity.

4 - Question

Which of the following relation is stated by Hooke’s law?

a) Stress is directly proportional to strain

b) Stress is inversely proportional to strain

c) Stress is directly proportional to square of strain

d) Stress is inversely proportional to square of strain

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Answer: aExplanation: According to Hooke’s law, stress is directly proportional to strain and the ratio of stress to strain is denoted by Y or E and is called Young’s Modulus oof elasticity.

5 - Question

Given the shear modulus(G) for aluminum as 2.4e+10 N/m2 and the shear strain is given as 6e-5. What is the value for shear stress?

a) 13.4e+5 N/m2

b) 14.4e+5 N/m2

c) 12.4e+5 N/m2

d) 13.4e-5 N/m2

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Answer: bExplanation: Shear modulus is the ratio of shear stress and shear strain. Therefore, if we simply multiply the shear modulus and shear strain we will obtain the shear stress. Hence the final answer is 2.4e+10 x 6e-5 which gives us 14.4e+5 N/m2 as the final answer.

6 - Question

Which of the following can be the value of Poisson’s ratio for an engineering structure?

a) 2

b) 0.4

c) 29

d) 100

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Answer: bExplanation: The Poisson’s ratio for most of the engineering structure normally lies between 0.3 and 0.6. Therefore 2, 29, 100 cannot be valid values for Poisson’s ratio.

7 - Question

If the Poisson’s ratio is given as 0.3 and the Young’s modulus is given to 7e10. What will be the value for shear modulus?

a) 2.69e10 N/m2

b) 3.00e10 N/m2

c) 2.59e10 N/m2

d) 2.72e10 N/m2

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Answer: aExplanation: The relation between Young’s modulus, shear modulus and Poisson’s ratio are given by v = E/2G – 1. Taking the 1 on the left side and rearranging we get G = E/2(1+v). Inserting the values given in the question the answer comes out to be 2.69e10 N/m2. Here E = Young’s modulus, G = shear modulus and v = Poisson’s ratio.

8 - Question

Stress strain curve for cemented tungsten carbide is:

a) Hyperbola

b) Parabola

c) A curve

d) Straight line

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Answer: dExplanation: The stress-strain curve for cemented tungsten carbide is a straight line as being a brittle material doesn’t have a plastic zone and therefore, it fractures after a certain load is applied.

9 - Question

Greater the angle of inclination of the stress strain curve less is the elasticity.

a) True

b) False

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Answer: bExplanation: IF the angle of inclination of a stress strain curve is high, the elastic zone of the material is more as the curve starts curving after the elastic limit. Hence the elasticity of the material is high.

10 - Question

Which of the following is found out by calculating the area under the stress strain graph?

a) Toughness

b) Hardness

c) Endurance

d) Strength

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Answer: aExplanation: Toughness is measured by calculating the area under the stress strain graph and is more for most ductile material than brittle material which has more toughness than ductile material.