TOPS Learning Systems, Pendulums 01. A washer swings on a thread, sweeping the face of a cereal box. This box is covered with a grid that measures length and amplitude. It is, in short, a classically simple TOPS learning system. Using a stopwatch and calculator, your students will graph length vs frequency into a beautiful curve; they'll stand this curve on its head by plotting the period, then straighten it back out by squaring the period. This straight line leads directly to a simple pendulum equation with powerful applications. Math teachers, don't miss this one!