Extreme Science: Penny Shine

What you will need:

  • Empty pop can or plastic pop bottle
  • Ruler
  • Pen or pencil
  • Scissors
  • Two bottle caps or plastic bottle tops
  • Hot glue gun
  • Adult supervision

Procedure:

This whistle can be made from an aluminum pop can or a plastic bottle.  If you choose to make it out of an aluminum can, please be VERY CAREFUL as the raw edges of the aluminum are very sharp which is why we have come up with the plastic version for this project.  Safety is ALWAYS our first concern.  These instructions will refer to using the plastic material.  If you are using the aluminum can, please just replace the word plastic with aluminum. Also, you will not need to use any glue if you are using aluminum.

  1. Cut a strip of plastic that measures ½” x 4 ½”
  2. Cut a 1” square of plastic.
  3. Fold your 1” square in half to create a crease, then open it back up.
  4. With your previously made crease pointing upward, place your 1” square on top of your plastic strip (centered, about 1” from the end) and fold the edges over the sides of the strip as shown.  Add hot glue UNDER the strip as shown to hold the edges in place.
  5. Now take the 1” end of the strip that is sticking out and fold it under so that it covers the edges of the square piece that you just glued in place.  Glue this in place as well.
  6. Curl the long end of your strip making sure to leave an opening or gap as shown.

  7. Your whistle will actually work as is but it can be a little tricky.  By holding it so that your fingers cover up both sides of the circular portion, if you get it just right, you can get it to whistle when you blow air into the mouthpiece.  This works a little easier if you used aluminum but can work with the plastic as well. Otherwise, you will probably want to cover the sides with your bottle caps.  To do this, make sure that the circular portion will just barely fit into your bottle caps.  Cut a section out of the side of both bottle caps to match the opening you created when you curled your strip.  Then, carefully glue the strip into your bottle caps to close the sides of your whistle as shown. 


    Note, if you are using plastic bottle caps, you may need to trim the edge or side so that they are no more than ½” each so that they will be approximately 1” thick when glued together.

    Please note that you will have to adjust the angle at which your mouthpiece is directing the air into your whistle in order for it to work properly.

What is going on?

Air is forced into the confined space of the cavity inside your whistle when you blow into the mouthpiece.  The air then whirls around inside the cavity until the pressure is so great that it “pops” out through the opening you created on the sides of the bottle caps.  Once the air pops out, it allows space for more air to enter into the cavity and starts the whole process over again.  The air entering and popping out of your whistle can pack and unpack 263 times per second!  The faster the packing and unpacking process, the higher the pitch.  The size of the cavity and the volume of air contained in the whistle will also determine the pitch or frequency of the sound that is produced.

Radical Rick

Extreme Science

www.ExtremeScienceFun.com

509-892-7621

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