A not-so-dumb idea...

Two days ago Rhett Allain tweeted this video:   

and said it would make for a good blog post.  I thought it would make for interesting class discussion.

So I showed the video in class.  I didn't say anything other than: "Here's an interesting video I thought we could watch."  After the video I asked the groups to talk about what they had observed and whiteboard everything they could think of to describe the physics displayed in the video.  Here are what 3 groups came up with.

The group that came up with "the tangential force caused angular acceleration" was pretty proud of that statement.  We talked about how using the concept of torque was probably better.  And, of course the best whiteboard was not photographed because I didn't get my phone before it was erased. That group not only identified the torque and angular acceleration, but the change in moment of inertia when the guy's leg came out of the seat and the change in center of mass which caused him to tip the chair over.  I was really impressed.

Thanks, Rhett!