This is going to be a short post because its a very busy week with multiple events and college visits on the schedule.  You can check out the post on momentum from the last time I taught physics for a more detailed discussion. We basically did the same experiments,  the only thing different is I asked the students to come up with their own experiment to show the conservation of momentum and did not give them any handouts.  Some students used the air track and gliders, a few used the hover soccer disks and one group used a Newton’s Cradle.

Here’s two photos from one experiment.  The first photo is a screen shot before the collision, with glider 1 coming in with a constant velocity from the left and glider 2 sitting at rest in the middle of the airtrack.  Both gliders have velcro on them so when they collide they will stick together.  The second photo shows the two gliders after the collision when they are stuck together and now moving at a slower velocity.  The red dots in the photos show the position of glider 1 throughout the experiment. Before the collision the dots are fairly far apart, but after colliding and sticking to glider 2, effectively doubling the mass of the object in motion, the velocity decreases,  indicated by the dots being much closer together.  Students were able to determine by analyzing the data that the velocity decreased by a factor of 2 as expected.

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Students read section 2.3 Bumper Cars in How Things Work, the Physics of Everyday Life and watched the following videos before class.