1. Elastic Force – Hooke’s Law
Physics 20
Elastic Force – Hooke’s Law

2. Elastic Force - Fs
When You stretch an elastic band, it will restore itself when you let go.
The same is true when you bend a tree branch or compress a spring.
This is called elastic force
Picture page SNAP

3. Hooke’s Law – the elastic force is directly proportional to the distortion (x) of the material
Equilibrium position – the position to which the elastic material will return.
Distortion – the distance of the object from the equilibrium position in (m).
k = the spring constant – the stiffer the spring the greater the spring constant and that stands to reason! Measured in (N/m)
Fs = -kx
The negative sign tells us that the elastic force is in the opposite direction to the distortion.

4. Example
A weight of 4.6N will stretch a vertical spring m. What is the spring constant?

5. Activity 9
Page 191 SNAP Book

6. Assignment Reading Questions Pearson Physics Pages 299 - 301
SNAP Pg 194: #’s 4-7