Mechanical Properties of Solids-
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Mechanical properties of solids are those properties of solids which define its solidity. OR Mechanical properties of solids are those physical properties that a solid exhibits upon the application of forces. |
Examples of Mechanical Properties of Solids are-
- Hardness
- Tensile strength
- Resistance to deformation
- Elasticity
- Plasticity
- Ductility and many more…
Rigid Bodies-
| The materials having a definite shape and size are called as rigid bodies. |
- A perfectly rigid body does not lose its shape or size under the influence of any external force.
- The distance between its molecules always remains the same under the action of any external force.
- There is no body which is perfectly rigid.
- The nearest approach to a perfectly rigid body are diamond, carborundum etc.
Deforming Force-
| An external force which changes the configuration (shape or size) of a body is called as a deforming force. |
- When an external force is applied on a body which is neither free to move nor free to rotate, the molecules of the body are forced to change their relative positions.
- Due to this change, the body may suffer a change in its shape or size.
- Such a force which changes the shape or size of a body is called as a deforming force.
Restoring Force-
| An internal force which helps to body to regain its original configuration after the deforming force acting on it is removed is called as restoring force. |
- When a deforming force is applied on a body, a force is developed within the body on account of relative molecular displacement.
- This force helps the body to regain its original configuration (shape and size) and is called as restoring force.
- This restoring force accounts for the elastic behavior of solids.
Elasticity-
| The property of a solid body by virtue of which it tends of regain its original configuration (shape and size) when the deforming force acting on it is removed is called as elasticity. |
For example-
If we stretch a rubber band and release it, it snaps back to its original length. So, it is elastic.
Types of Elastic Bodies-
| Those bodies which possess the property of elasticity are called as elastic bodies. |
Based on the degree of elasticity, the elastic bodies can be categorized under the following three types-
- Perfectly Elastic Bodies
- Partially Elastic Bodies
- Perfectly Plastic Bodies
1. Perfectly Elastic Bodies-
| A body is said to be perfectly elastic if it completely regains its original configuration (shape and size) after the deforming force acting on it is removed. |
- Since no body can completely regain its original configuration, so the concept of perfectly elastic body is only an ideal concept.
- The nearest approach to a perfectly elastic body are quartz fiber and phosphor bronze.
2. Partially Elastic Bodies-
| A body is said to be partially elastic if it regains its original configuration (shape and size) partially (not completely) after the deforming force acting on it is removed. |
- All the materials regain their original configuration partially on the removal of deforming force.
3. Perfectly Plastic Bodies-
| A body is said to be perfectly plastic if it does not regain its original configuration (shape and size) even slightly after the deforming force acting on it is removed. |
- Since every material partially regain its original configuration on the removal of deforming force, so the concept of perfectly plastic body is only an ideal concept.
- The nearest approach to a perfectly plastic body are paraffin wax, mud and putty.
Plasticity-
| The property of a solid body by virtue of which it does not regain its original configuration (shape and size) after the deforming force acting on it is removed is called as plasticity. |
When the elastic behavior of a body decreases, its plastic behavior increases.
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