Let's Make a Top

This past week, we did a small partner lab. Our mission was to make a top out of the following materials: 2 paper plates, a plain wood pencil, 6 pennies, and tape. The top also had to be able to spin for more than only a few seconds. However, there were no instructions other than to make a top. Immediately, each student in the room with his or her partner immediately began undergoing the engineering process, whether they knew it or not.

The engineering process has steps to be done in this order -- Define the problem, do background research, specify requirements, brainstorm solutions, choose the best solution, do development work, build a prototype, test and redesign. We already knew the problem, and we were presented with a top to look at in the back of the room, so we already defined the problem and did a little research on tops. The requirements were to make the top with the materials provided, and the top must spin for more than only a few seconds. We brainstormed quickly and then talked about our ideas on how to make the top. We then chose to mix our ideas together to get the best solution possible and we discussed who was to make it and walked through it together. Soon, we had a prototype and we were able to test that design. If it did not work that well, we tried something new. This lab, in a nutshell, was a little simulation of the engineering process!

This lab also shows a relationship between tops, angular momentum and moment of inertia. As the top spins, the angular momentum generated points straight up into the air, and if there were no friction, the top would spin forever because the momentum that holds the top up is forever conserved unless acted on by an outside force. The moment of inertia of the top is the rotational analog of the mass of the top. The angular momentum discussed above is the result of the top's moment of inertia times the rotational velocity.