[EricVanWyk]

Thanks again folks. The "lesson" ran without a hitch - I was surprised how effective it was! The goal of the exercise was to enumerate the design parameters that they could optimize, and in that respect it was perfect.

If you folks want to re-run it back at home, here is the 30 second overview of the 10 minute exercise:
1) Super brief intro to torque. We had a mix of students, many of whom had not taken any physics yet. Just enough meat to convince them that torque = force * distance.
2) Draw the box on the whiteboard, show the forces. Label everything that matters, nothing that doesn't.
3) Convert to torques.
4) Convince them that the box tips when the total torque is in the tipping direction.
5) Convert the torques to an inequality.
6) List the design parameters they can tweak at this point. Our first iteration was:
height of pusher
distance from center of gravity to pivot point
7) Break apart the second design parameter.
How can you move the center of gravity?
How can you move the pivot point?

((There was a 1 minute unscheduled brainstorm that I let run a bit, and then pulled back in. With 15 students, I didn't want them to move too far yet. I did not participate in the brainstorm.))

8) Brief reminder of friction, and understand that *in steady state and moving*, the pusher force is equal to the friction force. If it gets rammed, it exceeds friction.

9) Convince students that the formula that was F*d1 < W*d2 becomes W*u*d1 < W*d2. Cancel W.

10) From the new equation, list all design parameters:
height of pusher
center of gravity
pivot position
coefficient of friction
((Drivers ramming)) <- not really a design parameter, ish.


At this point I turned the meeting over to the student lead and stepped back. It was really neat to see how quickly they fixed their design, as a team. I'm sure a mechanical mentor could do a much better job, but this suboptimal way was effective and could easily be taught by any vaguely technical mentor.