SOM Notes

ME 217 – Strength of Materials

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SOM 2 Mark Question and Answers

2 Mark Questions and Answers:     UNIT –1

STRESS STRAIN AND DEFORMATION OF SOLIDS, STATES OF STRESS

1. Define stress.

When an external force acts on a body, it undergoes deformation. At the same

time the body resists deformation. The magnitude of the resisting force is numerically equal to the applied force. This internal resisting force per unit area is called stress.

Stress = Force/Area

When a body is subjected to an external force, there is some change of dimension in the body. Numerically the strain is equal to the ratio of change in length to the original length of the body.= P/A unit is N/mm^2

2. Define strain

Strain = Change in length/Original length   e = _L/L

3. State Hooke’s law.

It states that when a material is loaded, within its elastic limit, the stress is

directly proportional to the strain.

Stress _ Strain

_ _ e

_ = Ee

E = _/e unit is N/mm^2

Where,

E - Young’s modulus

_ - Stress

e – Strain

4. Define shear stress and shear strain.

The two equal and opposite force act tangentially on any cross sectional plane of

the body tending to slide one part of the body over the other part. The stress induced is called shear stress and the corresponding strain is known as shear strain.

5. Define Poisson’s ratio.

When a body is stressed, within its elastic limit, the ratio of lateral strain to the

longitudinal strain is constant for a given material.

Poisson’ ratio (μ or 1/m) = Lateral strain /Longitudinal strain.

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