APPARATUS Magnetic balance with two riders, mass balance for determining the mass of the riders, computer and printer, and spreadsheet and graphical analysis software. 2 92* 911 Mi Rider 112 F12 Figure 1: Magnetic Balance FR The magnetic balance consists of two similar ball-ended magnets, M, and M2 (see Figure 1). The balls on the magnets act as the magnetic poles we will study. Magnet M, is balanced horizontally at its center on a fulcrum about which it pivots; magnet M2 is held rigidly horizontal above the first in a vertically sliding clamp. The two magnets are arranged so that the right ball-end of magnet M2 is directly above the left ball-end of magnet Mr. Since these poles are the same type, i.e., both are either north or south poles, they repel each other with a force F12. A vertical scale attached to the base carries the sliding clamp and magnet M2. The sliding clamp allows the right pole of magnet M; to be positioned at various distances r12 above the left pole of magnet Mr. The right arm of magnet M, is notched to hold a small wire rider at equally spaced distances (0.01 m) along its length. The weight of a rider placed in any of the notches on the right arm of magnet M, produces a clockwise torque that causes the magnet to tip down to the right. Repulsive force F12 produces an opposing