String and Cup Phones

You will need:

  • 2 plastic or paper cups
  • String (20cm long and non-stretchy)
  • Drawing pin
  • Sellotape

What to do:

  • Using the pin, piece and hole in the center of the base of each cup.
  • Carefully thread one end of the string though the base of one cup and tie a knot in the end of the string
  • Taking the other cup, thread the other end of the string through the base and tie a knot to fasten
  • You need to be able to pull the string tight between the cups, so you may need to use a small amount of tape to secure the knots.
  • You should now have two cups on either and of the string, that each face away from each other.
  • Find a buddy, and take a cup each, stand apart so the string is pulled tight. Have one of you speak into the cup while the other has it placed over their ear. You should be able to hear each other clearly.

How it works:

The sound waves created by speaking into the cup causes the bottom of the cup to vibrate, these vibrations then travel through the string and into the base of the second cup. The base of the second cup will then vibrate and produce the same sound waves the speaker created. The listener can then hear the sound waves and therefore hear what the speaker said.

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