Continuing on in the science of sound, this month let’s build a telephone! I recall doing this as a child and found it fascinating (but then we didn’t have iPhones back then).
Materials:
- 2 plastic cups
- String (at least 6 feet)
- Something to make a small hole in the bottom of the cup (push pin, paper clip, etc.)
Experiment:
Punch a small hole into the bottom of the cup and feed one end of the string through the hole. Tie a knot at the end of the string that is on the inside of the cup or tie a knot onto a paper clip so that the string cannot come out of the cup when it is pulled. Do the same thing to the cup on the other end of the string. Pull the cups so that the string is taut and have one person talk into one cup while the other listens into the other cup.
What’s happening?
Last month we saw that it was vibrations that caused sound. This month we recognize that our voice is causing those sound waves and those waves travel through the air and into the string. The string keeps those waves moving over to the other cup and then into the air in the other cup and finally into your ear.
Extension:
Does it matter what kind of string you use (fishing line, yarn, wire, etc.)? Does it matter how long the string is? Does it matter what the cups are made of (paper, PETE, Styrofoam, aluminum or steel can, etc.)? Does it matter what size the cup is? Does it matter if the string is taut or loose? Can you use it with someone around the corner? What happens if you fill a cup with other things (cotton balls, crumpled paper, packing peanuts, etc.)?
References:
https://www.mombrite.com/string-telephone/
https://wowscience.co.uk/resource/the-science-of-the-string-phone/
To view past “ChemShorts for Kids” activities, go to:
https://chicagoacs.org/ChemShorts.
