#modphys: Students or Friction?

We spent this week on the a=F/m paradigm lab. Once the students got their data whiteboarded, I began to see some problems — serious problems. The close relationships I had seen during my practice runs were nowhere to be seen: instead, the students had graphs dominated by systematic errors and an assortment of unorthodox, confusing ways to represent their data.


The picture above looks alright, except that the reciprocal of the slope (about 0.4 kg) is rather different from the 0.2 kg one would expect. Other groups clearly had trouble getting consistent data.


And others clearly haven’t bought in to the idea of the course.


In the evening, I replicated their experiments, and got results akin to the first graph. Today, I re-did the experiment with my hover disc, with only moderate improvement. It seems that the modified Atwood machine really needs a dynamics track to work. Drats. Maybe next year I will try to build an air track with a shop vac.



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