Copyright © 2006, by The Science House (sciencehouse.ncsu.edu)

Martian Hat (Inertia)

Physics Concept This is an eye-catching and silly demonstration of the principle of inertia. An object can balance in a stable position when its mass is distributed evenly and when the center of mass is below the point the object is balanced on. Inertia is the property of an object that makes it stay at rest until a force makes it move.

Materials Two to three foot length of coat hanger wire or heavy gauge copper wire Two blobs of modeling clay or play-doh.

Method Bend the coat hanger into the shape shown in the figure and attach the two blobs of clay onto the ends of the hanger. Carefully place the balance point on the coat hanger onto the top of your head. Turn your head rapidly to face left. This will show the effect of inertia, that is, the blobs do not move when your head does. Do not jump when you turn your head.

Questions

Why is the Martian Hat stable atop your head? Why is the hat not stable when it is upside down? Does it matter what kind of hair do you have?