| Chronology | Current Month | Current Thread | Current Date |
| [Year List] [Month List (current year)] | [Date Index] [Thread Index] | [Thread Prev] [Thread Next] | [Date Prev] [Date Next] |
Of course it depends how one structures a 'pendulum' lab. In my classes, we start with looking at a ball swinging on a string and decide that we should take some measurements--perhaps this is a predictable, usable phenomena. The students decide what should be measured, what should be varied, together we work on a reasonably accurate way to time the motions, and then we go at it. I like to break this one into different groups doing different aspects--one studying the mass of the bobs, one looking at the angle of swing, three different groups looking at the length of the string--doing different ranges which I have 'cleverly' chosen such that each group's results will not be too inconsistent with a linear relationship but when combines clear show something else (we can do a 10 meter pendulum in our building) . Each group reports their results. After one lab they only come to the conclusions that the period doesn't depend on the mass of the bob, that the angle of swing matters, but not much below 30 degrees, and that the length matters. We return to the length data later to show that the dependence is with the square-root of L. We also get some help from a fictional 'theoretical' group (an infinite number of monkeys with computers) who have come up with a possible theoretical form that we can compare to our empirical fits. Since we have a constant and the monkeys have a constant based on 'g', we can see if our constants are consistent--actually get an experimental value for 'g' from our data--usually pretty close. Then only much later do we explain the angle dependence and the fact that the monkeys used SHM to derive their formula when in fact, the pendulum is only approximately SHM (swings less than 30 degrees).
That's the point: the pendulum is so very far unbalanced in
one direction that we can move a long ways in the other direction
before we achieve balance, let alone start worrying about unbalance
of the opposite kind.