# Mechanical Properties of Solids Class 11 Notes PDF

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## Mechanical Properties of Solids Class 11 Notes - Description

Adoration to all, Today we are going to upload Mechanical Properties of Solids Class 11 Notes PDF to help students. The notes of mechanical properties of solids class 11 are available here in PDF format and students can download it for free. Mechanical properties of Solids come under Properties of Bulk Matter. This entire unit is very important from an analysis point of view and carries a total weightage of 20 marks.

This chapter talks about various laws and concepts around solid bodies. The chapter is theoretically idiotic, so to learn them well students should understand the concepts first. To strengthen the understanding, physics class Class 11 chapter 9 notes include examples to explain the concepts clearly and logically. Students are advised to go through the notes of mechanical properties of solids class 11 regularly to maximize retention of the concepts and examples.

### Detailed Table of the Chapter 9 Notes –  Mechanical Properties of Solids Class 11 Notes PDF

 1 Board CBSE 2 Textbook NCERT 3 Class Class 11 4 Subject Science Notes 5 Chapter chapter 9 6 Chapter Name Mechanical Properties of Solids 7 Category CBSE Revision Notes

## Mechanical Properties of Solids Class 11 Notes PDF

1. Introduction

A rigid body refers to a hard solid object having a definite shape and size. However, in reality, bodies can be stretched, compressed, and bent. Even the strongest rigid steel bar can be deformed when a sufficiently large external force is applied to it. This suggests that solid bodies are not perfectly rigid. Solids have a definite shape and size. In order to make a change (or deform) their shapes or sizes, a force is always required.

1. Deforming Force:

A deforming force can be defined as a force that produces a change in the configuration (size or shape) of the object on application.

1. Elasticity:

Elasticity refers to the property of an object by virtue of which it regains its original configuration after having the deforming force removed. For instance, when we stretch a rubber band and release it, it snaps back to its original shape and length.

1. Perfectly Elastic Body:

The bodies which have the capability to regain their original configuration immediately and completely after having the deforming force removed are termed perfectly elastic bodies. Quartz fibre can be considered as a perfectly elastic body.

1. Plasticity:

When a body does not have the capability to regain its original size and shape completely and immediately after having the deforming force removed, it is called a plastic body, and this property is termed as plasticity.

1. Perfectly Plastic Body:

A body that does not regain its original configuration at all on the removal of deforming force is known as a perfectly plastic body. Putty and paraffin wax can be considered nearly perfectly plastic bodies.

1. Stress:

When an object gets deformed under the action of an external force, then at each section of the object, stress (an internal reaction force) is produced, which tends to restore the body into its original state.
7.1 Definition:
The internal restoring force produced per unit area of the cross-section of the deformed object is termed stress.
7.2  Mathematical Form:
Stress=Applied ForceAreaStress=Applied ForceArea
Its unit is N/m2N/m2 or pascal (Pa).
Its dimensional formula is
[ML−1T−2][ML−1T−2]
Types of Stress:
Three different types of stress are known. They are:
Longitudinal Stress:
When a deforming force is applied normally to the area of a cross-section, then the stress is termed longitudinal stress or normal stress. It is further differentiated into two kinds:

• Tensile Stress: When there is an increase in length of the object under the effect of applied force, then the stress is termed as tensile stress.
•  Compressional Stress: When there is a decrease in the length of the object under the effect of applied force, then the stress is termed as compression stress.
1. Tangential or Shearing Stress:

When the deforming force acts tangentially to the surface of a body, it generates a change in the shape of the body. This tangential force applied per unit area is termed tangential stress or shearing stress.

1. Hydraulic Stress:

When the applied force is due to a liquid uniformly from all sides, then the corresponding stress is termed hydrostatic stress.

1. Strain:

When a deforming force gets applied to an object, the object undergoes a change in its shape and size. The fractional change in their setup is termed a strain.
8.1  Mathematical Equation:
Strain=change in dimensionoriginal dimensionStrain=change in dimensionoriginal dimension
It is a dimensionless quantity and has no unit.
According to the change in setup, the strain is differentiated into three types:

1. a) Longitudinal strain=change in length original length) Longitudinal strain=change in length original length
2. b) Volumetric strain=change in volume original volume) Volumetric strain=change in volume original volume
3. c)Shearingstrain=tangential applied force area of force) Shearing strain=tangential applied force area of force
4. Hooke’s Law

Robert Hook observed that within the elastic limit, the stress turns out to be directly proportional to the strain. i.e.,
stress∝strain⇒stress=K. strain stress∝strain⇒stress=K.strain
where KK is the constant of proportionality known as the ‘Elastic Modulus’ of the material.
Here, it is to be noted that there are some materials that do not obey Hooke’s law like rubber, human muscle, etc.
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