1. Noadswood Science, 2012 Hooke's Law

2. Hooke’s Law To know Hooke’s law Wednesday, April 22, 2015

3. Watermelon (To Face)

4. Forces A force acting upon an object may cause a change in shape of the object… Some objects are able to recover their original shape when stretched (but some or not, if stretched too far)!

5. Hooke’s Law When a force is applied to an object it may be able to stretch and change its shape Any object which can go back to its original shape after the force has been removed is an elastic object Work is done to an elastic object to change its shape – this energy is not lost but stored as elastic potential energy The elastic potential energy is then converted into kinetic energy when the force is removed and the object returns to its original shape…

6. Experiment Your task is to investigate Hooke’s law… You need to work out the spring constant (k) for each of the springs The following equation will help: - F = k x e Where F = force; k = spring constant; and e = extension k = F ÷ e (so in this experiment using a known force divided by the extension of each spring will give the spring constant for each spring in the experiment)

7. Extension The extension of a stretched spring is directly proportional to the force applied F = k x e F = force (N) k = spring constant (N/m) e = extension (m)

8. Force Too Great There is a limit to the amount of force that can be applied to an object for the extension to keep increasing proportionally For small forces the force and extension are proportional, however there is a maximum force that elastic objects can take and still extend proportionally – this is the limit of proportionality (point P) If the force is increased past this limit the material becomes permanently stretched