Mechanical Hands

In the last post, you were promised some experiments involving mechanical energy that you can do with your own hands. Wait a minute, you might be saying, my hands aren't mechanical (I assume that none of you are robots!). Here's another case where scientists sometimes use words a little differently than most people do. Mechanical energy is simply the energy of moving objects. Your hands are objects, and when you move them, you are using mechanical energy!

The first experiment is very simple. Place your palms together and rub quickly. What do you feel? Why do your hands get warm? Your muscles create mechanical energy which turns into heat because of friction, which makes it hard to rub two things together. OK, that wasn't much of an experiment. Let's try another one...

Find a simple wire clothes hanger like the ones that come from the dry cleaner. If it is covered in paper, remove the paper. Grab the straight bottom of the hanger with one hand in each corner. Bend the straight part of the wire about eight to ten times. It may be hard at first, but will get easier. Touch the bent part of the hanger. It's hot! Again, your muscles supplied the mechanical energy, and the friction among the atoms in the metal created heat.

Can you think of any other examples of how mechanical energy can be turned into heat?