Imagine five empty match boxes positioned one right after the next. Push over the first match box and what happens? The first match box falls into the second. The second falls into the third. The third falls into the fourth…
Imagine the tiny particles (atoms and molecules) that make up a kite string. In a similar way, motion can be transferred from particle to particle. Although you can’t see this transfer, yet you can observe its effect using a string telephone.
Things Required:
Three paper cups
Kite string
Three paper clips
Pair of scissors
Pushpin
Some friends
Directions:
Use a pushpin to punch a hole in the bottom of each paper cup. Cut a segment of kite string about 20 feet long.
Pass one end of the string through the bottom hole of one cup. Tie a paper clip to the end of the string that projects from the inner side of the cup. Pull on the string so that the paper clip may lie flat against the inside bottom of the cup.
Place a second cup and paper clip on the other end of this string. Move the two cups apart so that the line between them may be pulled taut. Ask a friend to whisper into one cup. Place the other cup over your ear. Can you hear what your friend is saying? Reverse the roles. Can your friend detect your whispers?
Now cut a 10-foot segment of kite string. Place a cup and paper clip at one end of this line. Tie the free end to the middle of the two-cup line. Does this three-party line also transmit sound? How many more extensions can you add? Make a guess and then invite some friends to build a large string network.
This Is What Happens:
As one person spoke into the microphone cup, the movement of air struck the solid bottom of the cup, causing it to vibrate. This energy of vibration was transferred into the string. Like falling match boxes, the atoms of the strings passed the vibrations from atom to atom. Eventually, the string vibrations reached the listening cups. At these cups, the string movements were transferred to the cup bottoms. The vibrating bottoms set the air within the cup in motion. As this vibrating air struck your eardrum, you detected it as sound.