In real physics research, at least to get funding or beam time on a large accelerator, the scientist proposing the experimental study must present a model of the phenomenon which is to be studied. This model, in a mathematical form, includes descriptions of the interconnections between variables and is built on a few assumptions. It then provides predictions which can to be tested by the experiment. Usually, the models start out relatively simple, i.e. crude, and become more complicated and sometimes more sophisticated as data is accumulated and the assumptions are refined.

There exists such a model for the simple pendulum. It is based on a few simple assumptions, one being Newton's Laws of Motion. The second law of motion, usually known as F=ma, provides the physical and mathematical bases from which the following results are obtained (assuming the angle of release is not more than about 30° ):

a) the period does not depend on the angle of release.
b) the period does not depend on the mass of the pendulum bob.
c) the period does depend on the length of the pendulum. However, the dependence is not linear. The relationship is

T = 2 (L/g)^1/2

where T is the period, L is the length of the pendulum, and g is the acceleration due to gravity (a constant = 9.8 m/sec/sec).

8. Discuss ways to present your data which illustrate the interconnections or lack predicted by the model.

9. Compare your experimental results with the predictions made by the model.