Cup+and+String

The old "two cans and a string" technique really does work. The key is to make sure that the string is tight between the two cups, which means that the distance is limited and the two people have to be connected to each other by a straight line. As long as the string is tight, it works. This is a great way to understand how telephones and radios work.
 * Two Cups and a String**

Take two large paper cups and punch a tiny hole in the center of the bottom of each with a sewing needle or something similar. Take a piece of non-stretchable thread or kite string and put each end through each hole. Either knot or tape the string so it cannot go back through the hole when the string is stretched. Now with two people, have each one take one of the cups and spread apart until the string is tight. If one of you talks into one of the cups while the other listens, the person should be able to hear what the other person says.
 * How To**

When one person talks into their cup, the bottom of the cup vibrates back and forth with the sound waves. The bottom of the cup moving back and forth very quickly with the sound waves of the speaker's voice. The vibrations travel through the string by pulling the string back and forth. Therefore, the bottom of the second cup should start to vibrate back and forth just like the bottom of the first cup is vibrating, producing sound waves. The second person can hear the sound waves and can therefore hear what the first person says.
 * How it Works**

Justin media type="youtube" key="bp4Ge9RTJn0" height="315" width="560"

[] []