• String (twine works best)
• Paper cup
• Cup of water
• Red and yellow balloons
• Colored pens, pencils, crayons or paints
Time: 10 minutes plus decorating time
1. Cut a length of string three times the height of the cup. Then make a small hole in the bottom of the cup using scissors.
2. Push the string from the inside of the cup through the hole until you have 5 cm
of string poking through.
3. Tie a triple knot in the string at the base of the cup, and tape it down with sticky tape.
4. Cut a 3cm-by-3cm piece of dishcloth, and dip it in the cup of water. Wrap the cloth around the string inside the cup, and pinch it tightly between your thumb and pointer finger.
5. Decorate your cup to look like a chicken, duck, or any other animal that clucks. A balloon can be used to make a rooster’s crest.
6. Pull the cloth down the string a small distance at a time to hear your cup cluck!
All sounds are made by vibrations. When you pull down on the string, you cause it to vibrate, making noise. A vibrating string on its own is not very loud. When the string is attached to the cup, it causes the cup to vibrate as well. The cup causes more air molecules to vibrate, giving a louder sound.
This is how speakers work. A small cone causes a larger box to vibrate, amplifying the sound.
Ben Bravery and Tim O’Mahony work for Kexue Communications based in Beijing. They perform science shows and workshops for schools, birthday parties and other functions. Check out their website www.kexuecommunications.com or get in touch via email@example.com or 8415 5034.