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Krampf #479 High Bounce
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KRA-@aol.com
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Mar 22, 2007 09:18 PST
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Robert Krampf's Experiment of the Week
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The videos are up! The videos are up! After weeks of writing, taping,
editing, and wrestling with web servers, we finally have the first two Experiment
of the Week videos on my website. Please take a moment to watch them and
let me know what you think.
You can see them at: http://www.krampf.com/experiment_vid.html
Both videos are experiments from the first year of this list, and I am
posting the videos with revised text versions as well. Since the text has been
totally rewritten, I decided to use one of them, High Bounce, as this week's
experiment.
The High Bounce experiment was originally Experiment of the Week #31, written
September 19, 1997. At that time, the list was just starting to take off,
with me getting about a hundred new members each week. It was about this time
that I was discovered by the homeschool community. There were a few
homeschoolers on the list from the start, but at this point their numbers began to
grow. I started to change my writing style to focus on homeschoolers, students,
and parents instead of science teachers.
I have always liked this experiment because it makes students think about
energy in a fun way. You could spend hours with this one demonstration,
exploring forms of energy, how energy is transferred, inertia, and many other basic
concepts in physics.
This Week's Experiment - #479 High Bounce
Be sure to try this science experiment outside! It will save you the work
of cleaning up the pieces of broken lamps and shattered windows.
For this experiment you will need:
a basketball or soccer ball
a tennis ball
duct or masking tape
a flat, hard surface, outside
Hold the basket ball about shoulder high in one hand and the tennis ball at
the same height with the other. Drop both at the same time. If both are
fairly new and fully inflated, they should bounce about the same height. OK,
nothing strange about that.
Next, use the tape to make a round, raised collar on the basketball. This
is going to help you balance the tennis ball on top of the basketball. It
does not have to be fancy. Just a ridge of tape in a circle that will fit the
bottom of the tennis ball.
Hold the basketball out at the same height as before, with the tape ring at
the top. Place the tennis ball into the tape ring. It should balance there.
Now, before you drop it, think about what you expect to happen. Then drop
the balls.
Understanding the Science
What happened? The tennis ball bounced VERY high. Why did that happen?
When you were holding the basketball and the tennis ball, they had potential
energy, the energy of position. When you released them, that potential
energy was changed into the energy of motion. In other words, they fell. When
the basketball hit the ground, its momentum compressed it, flattening the
bottom. The same thing happened when the tennis ball hit the basketball. Their
energy of motion was changed into compressed mechanical energy, much like
squeezing a spring.
Then the compressed mechanical energy was changed back into the energy of
motion. As the basket ball bounced, it bumped into the tennis. That impact
transferred some of the energy of motion from the basketball to the tennis ball.
The basketball was left with less energy of motion, so it did not bounce as
high as it did the first time. The tennis ball wound up with a lot more
energy of motion, so it bounced very high.
What do you think would happen if you reversed the two balls, putting the
basketball on the top? How much higher would the extra energy from the tennis
ball lift it. What if you used a heavier ball instead of the basketball? Or
a ping pong ball on the top? There are all sorts of combinations to try,
and you will be surprised how much you learn while you are having fun.
Have a wonder-filled week!
Robert Krampf
Robert Krampf's Science Education Company
www.krampf.com
Who is Robert Krampf?
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