Experiment

Warning: If you are a kid, DO NOT let your parents read this! You'll find that your balloon is always popped! Why, you may ask? Keep going... you'll see.

1. Squeeze the hex nut through the mouth of the balloon. Make sure that the hex nut goes all the way into the balloon so that there is no danger of it being sucked out while blowing up the balloon.
2. Blow up the balloon, but be careful not to overinflate the balloon, as it will easily burst. Tie off the balloon and you’re ready to go.
3. Grip the balloon at the stem end as you would a bowling ball. The neck of the balloon will be in your palm and your fingers and thumb will extend down the sides of the balloon.
4. While holding the balloon, palm down, swirl it in a circular motion. The hex nut may bounce around at first, but it will soon begin to roll around the inside of the balloon. What is that sound? Could the balloon be screaming? The sound every parent loves...
5. Once the hex nut begins to spin, use your other hand to stabilize the balloon. Your hex nut should continue to spin for 10 seconds or more.

What happens when you change the size of the balloon or the size of the hex nut? Try using a marble instead of a hex nut. Does the marble make the balloon "scream?" Experiment with other objects whose edges may vibrate against the balloon.

How Does It Work?

This is actually a 2 for 1 experiment - you’re learning about the science of motion and sound. The hex nut circles inside the balloon due to centripetal force. Centripetal force is the inward force on a body that causes it to move in a circular path. It is a "center-seeking" force. A hex nut has 6 sides, and these flat edges cause the hex nut to bounce or vibrate inside the balloon. The screaming sound is made by the sides of the hex nut vibrating against the inside wall of the balloon.

To prove this, repeat the experiment using a penny in place of the hex nut (see The Spinning Penny experiment) . While the penny spins beautifully inside the balloon, the “spooky” sound is gone.   The Screaming Balloon makes for a great Halloween party giveaway or a fun science experiment for teachers to do in class.

Additional Info

Learn how to make a spooky, screaming cup and uncover the secret of "stick and slide" to create a vibration. It's also fun to experiment with a sound hose to make other "spooky" Halloween Sounds.