Try this easy experiment at home - find out how below!
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Noise Maker: Step-by-Step
What you need:
Paper cup
Cotton string, 30cm (12”)
Paper clip
Pencil
Water
Small cup
Paper towel
What you do:
Step 1: Poke a small hole in the bottom of the paper cup using the tip of the pencil.
Step 2: Tie the string to the paper clip.
Step 3: Push the free end of the string through the hole and pull it through the inside of the paper cup. Pull the string until the paperclip is resting against the cup’s base (on the outside of the cup).
Step 4: Fill the second cup with water.
Step 5: Fold a small piece of paper towel and dip it into the water.
Step 6: Pick up the first paper cup with one hand and hold it upside down. Make sure the paper clip is flat against the base (now at the top) and the string is dangling down. Reach inside the cup and press the damp paper towel around the string, while holding it between your thumb and index finger. Pull downward on the string in short tugs. What happens?
What’s going on?
The water on the paper towel creates friction between the paper towel and the string. This friction produces vibrations that travel up the string. When they reach the bottom of the cup, it starts to vibrate too, and this sound is amplified by the cup walls.
Now try this:
Different types of string or liquid will result in more or less friction between the damp paper towel and the string. Test different kinds of string, such as thread or yarn, as well as different liquids, such as soap or oil. Make hypotheses on whether or not these will make sounds. If they do, observe whether or not they sound different from the original string.
