The students above are using my newly acquired projectile launcher to test the range equation. They thought of a very clever way to find where the ball lands; looking for the mark on a colored whiteboard, as shown below.
The students below are trying to do circular motion by direct measuring the tension in the rope.
Today we started the lab aspect of deploying the Energy Transfer Model. We used this handout (modified slightly from the official U of MN lab for energy which is available in large PDF here). Students are asked to derive a formula for predicting the final velocity of a cart at the bottom of a ramp, and then we linearize the formula so the slope is 2g, which is pretty neat. The data works out pretty good. Next they will start planning their own verification lab.
Yesterday we took 10 minutes at the end of class to collect force of gravity vs. mass data. We whiteboarded it at the begining of the hour today, with a very convincing result that the slope is the gravitational field strength of earth, 9.8 N/kg. At the end of the hour we collected spring force vs. distance stretched data for springs, and we’ll whiteboard that after the long weekend.
We are working on testing the effect of mass on acceleration for a cart down a ramp, and students are going to write a lab report for this lab. One group came up with the great idea to keep all trials on the same screen, giving great qualitative evidence that the acceleration is not affected by the mass.
Today I was gone, and students were investigating adding mass to carts going down a constant incline. They apparently took it to the extreme.
I got permission from my principal 2 years ago to join a student created FB group with students in my class and it is awesome for community building and quick announcements. If you are not familiar with groups, you don’t have to be ‘friends,’ so we can’t see each other’s normal FB activity, only what is posted directly on the group page.
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.