Day 32: CAPM Lab PracticalPosted: October 11, 2013
Today we worked on a capm lab practical. We first found the acceleration of a cart down a ramp. Then we took down the motion detector and I showed them two photogates. The photogates measure the change in time between them (among other possibilities, but that’s all I showed them for now). The students must choose a starting location for the cart on the ramp that is at least 10 cm above the first photogate, then find where the two photogates should go such that the change in time was some particular value, different for each group. As you can see above, this went swimmingly in third hour. The other two, however, were failures on my part.
First hour I tried to go over a problem we worked on yesterday first, and then students didn’t have even close to enough time to do the problem and test it, especially because I only had one photogate setup that I had planned to move around to all the different ramps. In 2nd hour I skipped the problem at the beginning, but I still used different setups for each group and it proved impossible to move it around. For third hour we just found the acceleration of one setup as a class, then I gave them all different times and they only had to adjust the photogate location on the one setup to test. This worked MUCH better.
One thing that surprised me was how well this worked. The groups that did the calculation correctly were closer than a hundredth of a second off. It is very difficult to get the photogates in the right place, as they are 10 cm above the track. I figured there would be a bit more uncertainty; but the first group that did it right is the one that was right on, to the thousandth of a second! We all agreed there was a bit of luck in there.