Noisy vibrations make a clucking sound
Want to surprise your friends and family? With a bit of practice, you can make this cup cluck like a chicken!
You will need
- String
- Scissors
- Paper cups
- Wooden skewer
- Wooden toothpick
- Thin sponge
- Paper towel (optional)
What to do
Cut a piece of string about 60 centimetres long.
Put a paper cup upside down on a table.
Carefully poke a hole in the bottom of the cup with a skewer.
Use the flat end of the skewer to carefully poke the string through the hole.
Break the toothpick so you have a piece about 2-3 centimetres long.
Tie the piece of toothpick to one end of the string – either end will work.
Pull the other end of the string until the toothpick is on the bottom of the cup.
Slightly wet your sponge.
Hold the cup with one hand, and the sponge with the other.
Use the sponge to grip the string firmly, and then pull jerkily. If you do it right, you’ll make a loud, surprising, clucking noise!
Troubleshooting
If your cup doesn’t cluck, there are plenty of things you can try!
- Try squeezing the sponge harder or softer, and pulling the string faster or slower.
- Try using a damp paper towel instead of a sponge.
- Try wetting the string, and then pull on the string without a sponge.
- Try a different type of string. We found cotton string works well, and so did curling ribbon.
What’s happening?
As you start to pull, pressure on the string and sponge causes them to stick together. But as you pull harder and harder, the string stretches, the sponge bends and even the bottom of the cup starts to flex.
Eventually though, the force is too much and the string starts to slide through the sponge. The string relaxes, the sponge unbends, and the cup returns to normal while the sliding continues.
If everything is just right, the string and sponge will stick again just as everything unbends. Then it slips and sticks over and over, many times every second.
The slipping and sticking vibrates the string. But most of the noise comes from the bottom of the cup. It gets pulled every time the string sticks, and released every time it slips. The bottom of the cup vibrates back and forth like a speaker cone! The rest of the cup also works as a horn to direct and amplify the sound even further.
Did you know?
Have you ever pushed a chair across the floor, making a loud noise the whole time? Believe it or not, it’s making noise in a similar way to your clucking cup. Both are a matter of sticking and releasing, causing noisy vibrations.
If you’re after more science activities for kids, subscribe to Double Helix magazine!
Leave a Reply