Extreme Science: Penny Shine

What you will need:

  • Racquet ball
  • Sharp knife (adult use only)
  • ¼” wide strip of paper approx. 8” long
  • Glue stick
  • Dark marker
  • Scissors
  • Sand paper
  • Adult supervision


  1. Cut a strip of paper that measures ¼” wide and at least 8” long
    Add glue to one side of this strip of paper with the glue stick.
  2. Locate the center seam of the racquetball.  If you look closely, you can see where they have seamed two halves of the ball together to form the racquetball.  You may need to hold it in the light which will help highlight the seam.
  3. Carefully place the strip of paper around the ball covering this seam.
  4. Use your marker to make a line all the way around the ball on each side of the piece of paper as shown;
  5. Remove the piece of paper and have your Mom or Dad carefully cut the ball in half (between the two lines that you just drew) using a sharp knife as shown;
  6. Hold one of the halves of the ball in your hand with the opening facing AWAY from you, place your thumbs on the center of the ball and push while using your fingers around the outer edge of the ball in order to turn it inside out.
  7. Use the scissors to carefully cut around the edge on the line that you previously drew removing the (approximately) 1/8” excess material.
  8. Turn the ball back “right side out” by pressing the center of the ball back out to its normal position.
  9. Use your sandpaper to carefully sand the edge of the popper smooth.  This will take a little time and you must use caution not to remove too much material during this process step.  You want to remove enough material so that the popper will “pop” back out (from an inverted position) when dropped from about 4 feet from the ground.  To test this, simply press on the center of your popper as you did previously to turn it “inside out” then, hold it out in front of you so that it is parallel to the ground (with the inside of the ball facing up) and drop it.  If it just hits the floor and does not pop back up, you will need to remove more material.  Be very careful because if you remove too much material, the popper will not hold itself in the inverted position and you will have to throw it away and start over with the other half of the ball…..

What is going on?

Since the racquetball is made from a rubber substance that want to retain their shape, when you cut it in half and turn it inside out, it naturally wants to go back into its “normal” position.  By removing just enough of the material around the outer edge of your popper, you will find that you can now turn the popper inside out and it will just hold itself in this position.  When you turn it inside out, the part of the ball that is normally on the outside is now being forced inward causing the rubber material to be compressed, or pushed together.  The part of your popper that was originally on the inside of the ball is now being stretched creating tension on this section of your popper.  When you drop your popper on the ground, Newton’s first law of motion says that anything in motion wants to continue in motion until another force is applied.  Since the popper is turned inside out and the center of the popper is the highest point, the outer portion of your popper will hit the ground stopping it immediately.  Force is now applied to the center of you popper due to its inertia (wanting to continue in motion)  As soon as the center of the popper reaches a point where the compression and tensions can pull it back into its normal position, the center “pops” down hitting the floor with enough force to propel it upward extremely quick!

Try this:

Try throwing your popper similar to how you would throw a Frisbee to see if you can get it to hit flat on the floor in a desired location.  Once you do, it will POP straight up from there.  Also, try different surfaces.  I have found that these work really well on my hardwood floors and on a smooth concrete surface, yet they do not fly near as high when I toss them on my driveway which is not as smooth.

Radical Rick

Extreme Science



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