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From Liz Gire Spring 2016:

The commands are initially hidden and need to be expanded using the far right hand bracket. Students take a long time to figure (if ever) that the FIX or ROT command inside the brackets determines whether or not the initial velocity is with respect to the fixed or rotating frame.

In the future, I would try starting with a motion diagram of linear, constant speed motion and transparency with a coordinate system on it. I'd have the students draw the new motion diagram (on the transparency) that arises as they rotate the coordinate system between time steps. Then, after this, have them look at the mathematica notebook. I think this would help students to interpret what they are seeing on the mathematica animation.