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How to Make Walkie-Talkies Out of Cups

You can teach children about sound waves with a hands-on -- and ears-on -- project by making walkie talkies out of a pair of paper cups and a piece of string. The sound vibrations created when a child talks into one cup travel through the string and are reproduced in the second cup. This demonstrates the physics behind how sound travels from one point to another, and it can set the stage for more advanced lessons in sound waves or physics in general. Best of all, the children will be having fun while they learn.

Things You'll Need

2 paper cups
Nail
Toothpick
String,10 feet long

Instructions

- 1
  Make a hole in the center of the bottom of each paper cup with a nail. Pierce the cup from the inside.
- 2
  Break a toothpick in half. Tie one end of a 10-foot length of string around one of the toothpick halves, making a secure knot. Thread the other end of the string through the hole in one of the cups from the inside, then pull the string through the cup until the piece of toothpick rests against the bottom of the cup.
- 3
  Thread the string through the second cup from the outside and pull about a foot of string through the cup. Tie that end of the string around the other toothpick half, then pull the slack back through the cup until the piece of toothpick rests against the bottom of the second cup.
- 4
  Give the cups to two people and have them step apart from each other until the string between the cups is taut.
- 5
  Have one person place a cup over his ear, then have the second person speak into his cup. The sound will vibrate the string, allowing the person with the cup over his ear to hear what the speaker is saying.

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