Build a String Telephone
Ever wonder if you can actually use tin cans to make a telephone? Let’s try it and see!
What you need:
• Paper or styrofoam cups
1. Tie a toothpick on each end of a length of string.
2. Poke the toothpick through the end of the cup.
Pull the string tight so the toothpick rests on the inside bottom of
the cup. Put one cup at each end of the string. (You may want to
experiment with different cups and strings to see what works best.)
3. Hold the string tight and talk into one of the
cups. The person at the other end should be able to hear you. Why does
the string have to be tight?
4. Try to make a party line by tying a third string
and cup onto the middle of the string. Can everybody talk to everybody
What’s going on?
Sound waves need something to travel through. Usually they travel
through air, but they can travel much faster and farther through a
string. The string has to be tight or else the sound wave can’t travel
through it. The cup helps to amplify the sound on the other end.
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