Stress And Strain - Practice Questions & MCQ

NEET 2023 Answer Key Available Code H1, H2, H3, H4, H5, H6 - Download Solutions PDF

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Stress and it's types is considered one of the most asked concept.
17 Questions around this concept.

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A film of water is formed between two straight parallel wires, each $10 \mathrm{~cm}$ long and at a separation of $0.5 \mathrm{~cm}.$ The work that must be done to increase the separation between the wires by $1 \mathrm{~mm}$ is (surface tension of water $\mathrm{=7.0 \times 10^{-2} \mathrm{Nm}^{-1}}$ )

$\mathrm{7.0 \times 10^{-5} \mathrm{~N}}$

$\mathrm{1.4 \times 10^{-5} \mathrm{~N}}$

$\mathrm{7.0 \times 10^{-7} \mathrm{~N}}$

$\mathrm{1.4 \times 10^{-7} \mathrm{~N}}$

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A cubical block of mass ' $m$ ' and side ' $a$ ' is placed on a rough inclined plane of inclination $\theta$ . The direct and shear stresses in the block are _____

$f_d=\frac{m g \cos \theta}{a^2}, f_s=\frac{m g \sin \theta}{a^2}$

$f_d=\frac{m g \sin \theta}{a^2}, f_s=\frac{m g \cos \theta}{a^2}$

$f_d=\frac{2 m g \cos \theta}{a^2}, f_s=\frac{2 m g \sin \theta}{a^2}$

$f_d=2 m g \sin \theta, f_s=2 m g \cos \theta$

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Concepts Covered - 2

Stress and it's types

When a force is applied on a body, it is deformed to a small or large extent depending upon the nature of the material of the body and the magnitude of the deforming force.
The internal restoring force acting per unit area of cross-section of the deformed body is called stress and is denoted by σ.
The magnitude of stress, $\sigma =\frac{F}{A}$
Unit of stress: $N/m^2$ or Pascal(Pa)
Dimension of stress: $[ML^{-1}T^{-2}]$
Types of stress:

Longitudinal stress/ Normal stress: In Longitudinal stress, the force is applied normal to the surface.

It is of two types:

Tensile stress: Longitudinal stress produced due to increase in length of a body under a deforming force is called tensile stress.
Compressive stress: Longitudinal stress produced due to decrease in length of a body under a deforming force is called compressional stress.

Fig: Tensile Stress Fig: Compressive Stress

Shearing stress/ tangential stress: if two equal and opposite deforming forces are applied parallel to the cross-sectional area of the cylinder, there is a relative displacement between the opposite faces of the cylinder. The restoring force per unit area developed due to the applied tangential force is known as tangential or shearing stress.

In this case, deforming force is applied tangential to one of the faces.
Area for calculation is the area of the face on which force is applied.
It produces change in shape, volume remaining the same.

Fig:- Shearing stress

Volume stress:

It produces change in volume and density, shape remaining the same.
It occurs in solids, liquids or gases
In case of fluids only bulk stress can be found.
It is equal to change in pressure because change in pressure is responsible for change in volume.

$Volume \ \ stress= \frac{F}{A}=P$

Strain and it's types

Strain is defined as the ratio of change in configuration to the original configuration.
It has no dimensions and units as it is the ratio of two similar kind of physical quantities.
Types of strain:-

Longitudinal strain:- If the deforming force produces a change in length alone, the strain produced in the body is called longitudinal strain.

If the length increases from its natural length, the longitudinal strain is called tensile strain.
If the length decreases from its natural length, the longitudinal strain is called compressive strain.

$Longitudinal\ strain=\frac{\Delta L}{L}$

Fig: Tensile strain Fig: Compressive strain

Shear strain:- If the deforming force produces a change in the shape of the body without changing its volume, strain produced is called shearing strain.

It is defined as angle in radians through which a plane perpendicular to the fixed surface of the cubical body gets turned under the effect of tangential force.

Fig:- Shearing strain

$Shearing \ strain=\frac{\Delta x}{L}$