**PURPOSE: **To show that pendula of different length suspended from the same point rotating at the same angular speed rise to the same vertical height.

**DESCRIPTION: **When the device is rotated at an angular speed *w* the angle *a* from the vertical which a pendulum of length *l* will assume is given by cos *a* = g /* w*^2 *l*, where g is the acceleration of gravity. The vertical distance of each from the support point is* l* cos *a* = g /* w*^2, the same value for each of the pendulum. This can be easily observed using the apparatus.

**SUGGESTIONS: **Accelerate slowly, then maintain constant angular speed.

**REFERENCES: ** (PIRA unavailable.) This is a sample problem, Halliday and Resnick, Fundamentals of Physics, Vol. 1, third edition, pages 112-113.

**EQUIPMENT: **Base from rotating stool, rod, three golf balls on strings, and guide wires.

**SETUP TIME: **10 min.