Question
What is stress and what is its origin?
Solution
When an external force is applied on the body there is a deformation in it's shape. The deformation in the shape is due to relative change in the position of atoms or molecules. This relative change in the position causes the attractive or repulsive interatomic or intermolecular forces to set up in the solid which is called restoring force. This restoring force is the origin of stress. The restoring force per unit area is called stress.
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