10. A Set of CM Demos

a. An irregularly sharped wooden block is suspended from various points, and a plumb line is dropped to determine the center of gravity.

b. A double cone will roll up an incline. (Actually the axis or c.m. of the cone descends because of the divergence of the rails.)

c. The leaning tower is unstable with the top in place, but stable when the top is removed.

d. Hold your belt up with an otherwise unstable plastic bird.

e. A dumbbell with unequal masses on the end of a rod is suspended by s string to locate the center of mass. The dumbbell can then be tossed across the lecture hall to show that the center of mass follows a parabola, even though the ends are flying around. The center of mass is marked with phosphorescent paint which can be activated by ultraviolet light. Then in total darkness the students can see the dimly marked center of mass flying across the room in a parabola.