This document defines and explains key concepts related to elasticity, including Hooke's law, stress, strain, and the Young modulus. Hooke's law states that the extension of an elastic object is proportional to the applied force up to the limit of proportionality. Stress is defined as the external force acting on an object per unit of cross-sectional area. Strain is the ratio of extension to original length. The Young modulus is the ratio of stress to strain and provides a measure of an object's elasticity.

1. Elasticity

2. Objectives
• Elasticity
• Hooke’s Law
• Stress
• Strain
• Young modulus

3. • Elasticity :
•
is a property of object to deform when a force is applied and
to return it’s original shape when the deforming force is removed,
• e.g. rubber band, spring
• Plastic Deformation
• when the deforming force is removed, the object doesn’t return to it’s
original shape
• e.g. Plastine, Blu-tack

4. • Hooke’s law:
‘The extension of a body is proportional to the force causing it
provided that the limit of proportionality is not exceeded’
Extension:
when a force is applied it changes the length of the object
the change in length is called extension
Limit of proportionality :
The greatest force that can be applied to an elastic body without ca
using permanent deformation.

7. • Force (y axis)
• Extension (x axis)

8. • Stress:
is a quantity that is proportional to the force causing a
deformation. Stress is the external force acting on an
object per unit cross sectional area.
Stress is the load per unit cross-sectional area of the material
Stress (Nm-2) =
force (N)
cross-sectional area (m2)

9. • Strain:
is the ratio of extension to original length.
Strain =
extension (m)
original length (m)
There isn’t any unit of strain.

10. • Young modulus :
the ratio of stress to strain.
Young Modulus (Nm-2) = stress
strain
or
E = stress
strain

13. Questions….

14. Thanks……