Principal axis theorem

The principal axis theorem is like a magic trick that lets you rotate an object and figure out which way it will move. It is like spinning a top and knowing which way it will tumble.

When you look at an object, there are three axes, like three imaginary sticks sticking out of it. One of them is the longest and the other two are shorter. When you spin the object around these axes, one way it spins smoothly like a top, but the other two ways it wobbles and tumbles.

By using some special math tricks, we can figure out which of the three axes will make the object spin smoothly and which ones will make it wobble. This helps us figure out how the object will move when we rotate it around different axes.

This magic trick is very useful for scientists and engineers who work with objects that spin or move around in space. It helps them understand how to control the movement of these objects and make them go where they want them to go.