9.1.P11

Initial observations of the oscillation of a pendulum on the end of a rigid rod reveals that the detailed structure of the angle of the rod as a function of time is fit very well by a function of the form

θ(t) = θ₀ cos(ωt + φ).

Yet subsequent more extensive observations give convincing evidence that this cannot be a good representation of the motion for long time periods. Explain what observation leads to this conclusion and resolve the apparent contradiction.

Joe Redish 10/30/02