Science Buddies: "Ask an Expert"

So I have a question that I have always wondered. To start, we must first look at an example. Take a pencil balanced half on a table and half off a table. You gently tap on the end off the table so that the end on the table rises the same distance. How fast did the transfer of motion occur from each end of the pencil? Do different substances have unique transfers of motion depending on atomic properties? Would this be a good science project? Where would I start??

Thanks so much for your help!


Sincerely,

Ben

Bshapiro - Your example is interesting and I believe you sense that the rising end of the pencil lags (in time) the motion of the end you tapped in the downward direction. This is very imperceptible but true. There will be some flex of the pencil over the fulcrum (edge of the table), and the rising end of the pencil will occur slightly later. Momentum will continue as the pencil flexes upward, and the pencil will continue some oscillation for a short number of cycles. Most of this is a function of the mechanical properties of the wood, not necessarily on atomic properties. The phenomena would make an interesting experiment, but I think the measurement equipment needed to observe this might be out of range. Other similar approaches might use springs, masses etc. to show some of the motion aspects but slowed down considerably to be more observable. Good luck.

Rick Marz