This is an updated slideshow of the one I made in 2014 for my Curiosity Machine program. We did the balloon helicopter challenge on the CuriosityMachine.org website and learned about elastic energy.

1. Hands-on Science and
Engineering at Pasadena
Public Library
April 25, 2018

2. Energy cannot be created or
destroyed; it can only be converted
from one form to another.

3. • Potential Energy is the energy possessed by an object by
virtue of its position or condition
• Gravitational Potential Energy is the energy of an
object due to its position in a gravitational field
• Elastic Potential Energy is the potential energy stored
when something is stretched or deformed
• Kinetic Energy is the energy possessed by an object by
virtue of its motion
• Mechanical Energy is the total energy in a system, the
total kinetic energy and potential energy stored in an
object
http://physics20project.weebly.com/unit-4-work-and-energy.html

4. The bow and arrow is one of the
first tools humans made to use
elastic energy to do work.
The farther you pull on the bow,
the greater elastic potential energy
you store.
Also, pulling on the string of a bow
changes its shape, which increases
its elastic potential energy.
When the arrow is released, elastic
potential energy converts to kinetic
energy and the arrow flies!

5. Can you name some other examples of elastic
potential energy?
https://scratch.mit.edu/projects/31671030/#player

6. Balloons expand when you fill them with air, but if you give the air an
opening through which to rush out, the balloon will contract, also moving
away from the direction of airflow. Energy!!

7. Build a propeller-powered balloon helicopter!

8. (But keep in mind that
while these blades are
massive, they also have
a powerful engine
making them turn very
rapidly. We will need to
scale our blades down a
lot in order to allow
them to turn freely and
super fast.)

10. Pull a paperclip apart into a straight steel wire and cut
your blades out of paper (paper plates work but I
discovered that paper is lighter!!) and attach them to
either end of the paperclip. Pull a rubber band around
one of the blades so that it hangs between them.

11. I have already made
“motor casings” for you by
gluing a flat metal washer
to a boba straw. This is
easy to make at home too.
Use a strong glue, like a
glue gun. The washer will
reduce friction from the
propeller.
This casing is going to
contain the twisted up
rubber band, which will be
the “motor” of your
elastic energy machine.

12. Next you will use your skewer to push the rubber band
through your boba-straw-and-washer motor casing.
Stick the skewer through the rubber band where it
sticks out from the straw (cut your straw shorter if you
need to). Now you have created an elastic motor!

13. Please note: my last few slides showed an early version
of this project using paper plates. The
CuriosityMachine.org website also recommends paper
plates.
But I wasn’t getting the right speed with my paper
plates. Once I realized that what I wanted was for my
blades to spin really fast, I experimented with different
materials to see what would spin the fastest, and
construction paper won. It’s lighter, has less drag, and
still manages to work up a good amount of wind.

14. Attach helium balloons to the wooden
skewer. I found that I needed to tape
my balloons down to each end of the
skewer, for several reasons:
1. If the balloons’ strings are left
loose they will take away too
much of the elastic energy. And
then your blades won’t turn, but
your balloons will!
2. You also don’t want the strings
getting in the way, halting the
motion of your blades. If anything
touches the blades, they will stop.
3. It makes it so that there is less
movement from the balloons
overall, so the energy has to go to
the propeller because there is
nowhere else for it to go.