Both the accelerometer and video camera seem equally useful in calculating the angular velocity of the merry-go-round but since the positions of the people on the MGR (especially the outer positions) are critical, the video camera is a better single tool for doing the experiment. This field trip to experiment on the merry-go-round was a great way to experience rotational motion and provide an opportunity to test physics principles outside the laboratory. You can see a QuickTime movie of our experiment at http://physics.bgsu.edu/~vanhook/mgrexperiment. We encourage you to show this to your students if you can't bring them to a playground to do the experiment for themselves. Some key experiences we had were:

We were surprised how difficult it was to move inward when the MGR was rotating. Quite a large force was required on our part to stay on the MGR or move inward (F = ma_c = m²r), which in our experiment was approximately equal to our weight.

It was very real to us that we were doing work—exerting a force over a distance—when we tried to move inward as the MGR was rotating.

We discovered that we wanted to be the first person to move inward, since it was even harder for the second person because the MGR's angular velocity had increased due to conservation of angular momentum.

We discovered that a MGR has quite a lot of rotational inertia and in practice that means that it's not easy to stop. (See the video for what happened to one of us when he first tried to stop the MGR rotating.)

Unfortunately, due to insurance issues more and more parks are retiring their merry-go-rounds. For example, the merry-go-round that we used was removed from the park a few months after we filmed our experiment.