Introduction ( mechanical properties of solids )

• This lesson is focussed on how we stretch, compress and bend a body.
• We have seen that if we stretch a rubber and let it go it deforms but by applying the force, it again regains its original shape.
• If we take an aluminium rod and apply very strong external force on it, the shape of the rod might change but it does not regain its original position.
• We will take a look why some materials are elastic and why some are plastic.

Solids and their mechanical properties

• Mechanical Properties of solids describe characteristics such as their strength and resistance to deformation.
• It describes about the ability of an object to withstand the stress applied to that object. Objects also resist changing their shape.
• For example:- Objects such as clay can be easily deformed so they have less resistance to deformation but objects like iron don’t change their shapes easily. When heated they change their shapes which means they have very high resistance to deformation.

Mechanical properties:-

1. Elasticity: – Elasticity is a property by virtue of which original shape is regained once the external force is removed.

• This means it tells us how much elastic a body is.
• For example:- A spring .If we stretch a spring it changes its shape and when the external force is removed spring comes back to its original position.

2. Plasticity: – Plasticity is reverse of elasticity.

• Property means permanent deformation.
• The object never regains its original shape even when the external force is removed. These types of objects are called as plastics.
• For example:- Toys, Buckets made up of plastics.