Student "edition" found at {csi dot journalspace dot com}.

Maybe I shouldn't have started this blog now, not with everything that's been going on.


For the first day of the eighth week of classes, in my mechanics laboratory session, we had the fourth experiment, which is Atwood’s Machine.

In fact, in the quiz, one of the questions was the title of the experiment in the manual (different from what was posted in their lab report assignments), which is Newton’s Second Law.

The other three questions in the quiz were about the equations for experimental and theoretical acceleration, and the composition of the unit introduced in the experiment – dyne, which is one gram centimeter over second squared.

Some argued that it should still equal one Newton, but I said a kilogram is a thousand grams while a meter is only a hundred centimeters, and both are in the numerator, so they don’t cancel out. One Newton is actually one hundred thousand dynes.

Since no one has gotten perfect in the quiz yet, I told the students that just like in a popular elimination quiz game show each consecutive perfect score they get in the quiz from this point on would only double the total of their total perfect quizzes.

For the first time, we were using newly ordered and purchased wide diameter (about three inches across) pulleys that finally prevented the two weighted pans from colliding into each other as one went up and the other was pulled down by gravity.

I also had to give new values for the two masses to be used, based on the 530 grams total of weights in each set given to the groups. At twenty grams switched from each set of trials, the last was 270 and 260 grams, and the first was 350 and 180 grams.

I reminded the groups that the performance of the part where measurements should be made would only take less than thirty minutes, so there was no need for them to take up the whole three hours as they are wont to do.

The groups complained though that in the last trial, the pans wouldn’t even move. Okay, so the large pulley wasn’t as frictionless as we thought.

280 and 250 grams didn’t work either, but 285 and 245 grams did. Maybe I’ll use that next time, and just move fifteen grams from one pan to the other for each trial.

Wow, as usual, I’m already planning for next term. A teacher’s preparation is never done.

Session 837’s pulley doesn’t move anymore at this point because of the near equal weights on each pan. Class dismissed.