Homemade Hooke’s Law Device
Posted March 5, 2012on:
I like saving money for my school. Nothing against Carolina Biological, we’ve been really pleased with their equipment and service, but sometimes their stuff is just way overpriced. Their Hooke’s Law Device is $35 each. I made a similar set of devices for a couple of dollars using what we already had in the lab and classroom.
My device is made with a ring stand and small rubber bands to hold a ruler in place. I used a pendulum clamp as the top support, but any clamp will do. To connect everything, I used a bit of chain that comes with a shop fluorescent lamp and opened up the links. These are in an S shape and twisted to be offset by 90 degrees. You could just as easily purchased a package of S hooks at Home Depot for a couple of dollars. At the top, I hang one side on the clamp and hook the spring over the other opening. Same on the bottom, the hook provides a place to hang a weight.
We use hanging weight sets, I just didn’t have them hand for the picture, this is one of my 500g medicine bottle weights. The springs come from Harbor Freight. They have a box set of 200 springs for about $5. Lots of springs to play with, many look alike but have very different spring constants.
My “indicators” were fabricated on the 3D printer, but you can just as easily make the same thing with two Popsicle sticks and some glue. Drill the holes or it will split.
That’s really the whole thing. I found that if I spun the whole setup one rotation CCW, the spring would try to rotate clockwise, holding the indicator against the ruler and making it much easier to read.
I’m planning on adding a scatter chart to this lab. The students will enter the points in Excel to create the chart and then plot a trendline. We can then use the first order trendline to determine an unknown weight based on the distance the spring stretched. This setup was inexpensive and effective.