Extreme Science: Inertia Sticks

What you will need:

  1. (2) small funnels
  2. 1- Approximately 3 inches in diameter
  3. 1- Approximately 2 inches in diameter
  4. 24 inch length of Vinyl tubing – Approximately 3/8 inch inside diameter.  Funnels should fit snugly into ends of tubing.
  5. 9 inch diameter balloon
  6. Scissors
  7. Human with a heartbeat
  8. Adult supervision (can also double as the human with a heartbeat)


  1. Insert the small end of one of your funnels into one end of the tubing.
  2. Insert the small end of your other funnel into the other end of your tubing.
  3. Carefully cut the “mouthpiece” section off of the balloon, about where the balloon begins to get bigger/round.
  4. Stretch your balloon over the top opening of the larger funnel making sure it is stretched tight and smooth.
  5. Place the funnel with the balloon over your heart which is located on the left side of your chest.
  6. Place the smaller funnel up against your ear and listen carefully.  That “thump, thump, thump” that you hear is actually your heart pumping blood through your body!

What is going on?

Sound is vibration.  When your heart pumps blood through your body, it creates a “thumping” sound with each pump.  Doctors can use their stethoscopes to listen to our hearts which help them to determine our health.  By placing the balloon over the end of your stethoscope, this allows the air inside of your stethoscope to carry sound due to vibrations.  The air molecules actually vibrate and will carry the sound all the way up the tube to your ear!

Try this:

Although your stethoscope is not as sensitive as the one your doctor uses, try listening to other functions such as your lungs or even your intestines after dinner!  See if you can hear your body digesting the food you just ate.  You can also try whispering toward the balloon covered funnel and see how well you can hear yourself.

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