Screaming Balloons
What would Halloween be without spooky sounds? Here's an
easy-to-do experiment using only a balloon and a hex nut from
the hardware store. Be sure to buy enough supplies for all of
your Halloween party guests because everyone is going to
want a screaming balloon!
Materials
You’ll need good quality latex balloons (9" to 11" in size) and
some 1/4" hex nuts from the hardware store.
Experiment
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. Blow up the balloon, but be careful not to over inflate
the balloon as it will easily burst. Tie off the balloon and you’re
ready to go.
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. 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? 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.
How does it work?
This is actually a 2 for 1 experiment - you’re learning about the
science of inertia 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. The
old concept of “centrifugal force” (an outward or center fleeing
force) has been largely replaced by a more modernistic
understanding of “centripetal force” (an inward or center
seeking force). The 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. While the penny spins beautifully inside the
balloon, the “spooky” sound is gone. Experiment with different
sizes of hex nuts or any other circular object whose edges
might vibrate against the balloon and create a spooky sound.
The Screaming Balloon makes for a great Halloween party
give-away or a fun science experiment for teachers to do in
class.
Experiment From Steve Spangler Science
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