1. Elastic Objects

2. For a spring, the amount the spring is stretched or compressed (x) is directly proportional to the amount of force applied
F = kx k – spring constant
Spring constant depends on the individual spring
Stiffer spring – higher value of k

3. Graph For any spring, the graph of F vs x shows a direct proportion
Slope is k
Units of k = N/m

4. When the spring is released, it gives off the same amount of force but in the opposite direction
Fs = -kx Hooke’s Law

5. Elasitic Potential Energy
Work done by an elastic object
PEe = ½ kx2
Since work is a change in energy
W = PEe2 - PEe1

6. Example
A vertical spring is stretched by 5.5 cm when a 500g mass is attached to it.
a) find the spring constant
b) what potential energy is stored by the spring?
c) how much work is done in stretching the same spring from 3.0 cm to 10 cm?