Hooke's Law states that the extension of a spring is directly proportional to the force applied. It can be written as Force = Spring Constant x Extension. Young's Modulus is a material property that indicates how much a material will deform under stress. When stress is applied to a metal, the positive ions will spread apart as the atomic bonds stretch like springs. If the metal is within its elastic limit, it will return to its original shape when the stress is removed.

1. Hooke’s Law and Young’s
Modulus Revision

2. Define these terms:
• Stress
• Strain
• Extension
• Length
• Compression
• Tension

3. Hooke’s Law
This is the
force applied This is the
(N) extension (m)

4. We can write it another way
This is the
This is the extension of
This is the gradient (N/m)
force applied the spring
and is unique (m)
(N) for each spring

5. Young’s Modulus

6. Elastic Movement in Metals
Atoms are stacked in planes as +ve ions in a sea of
-ve free electrons.
When stress is applied to the metal, the +ve ions
will start to spread apart.
The atomic bonds stretch, and the attractive forces
between the atoms will oppose the applied stress,
like millions of tiny springs.
If the metal has not yielded, the interatomic forces
will pull the metal back into its original shape when
the stress is removed.

7. Elastic Movement in Metals