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I think the article and issued raised are excellent. I also teach and the research presented here helps one to re-evaluate our confidences and the effect of our teaching on students. Great work!

I would like to point out that the solution to the ball leaving the coiled path mentioned in the article is likely not correct. If a ball was in a channel of such shape it would leave with some spin imparted on the ball through interaction (friction) with the sides of the channel. Note that as a ball moves through the channel the outer most edge of the channel has a longer path length than the inner side of the track. Thus the ball would leave the track with some spin (think of a curve ball thrown by a pitcher). The spinning ball would interact with the air and NOT travel along path B as you indicated in the article. I would specify in the question that this experiment takes place in a vacuum as without air the spin of the ball will not influence the trajectory and then the answer would indeed be a straight line.

I had a good laugh because I would have undoubtedly picked answer “C” and been quite confident in my answer and then been lumped into those who were wrong but confident. It would be easy enough to perform the experiment to empirically observe the correct answer.