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Cotton Ball Launchers


Students will be introduced to the concepts of conservation of energy as well as potential and kinetic energy by building and testing a homemade cotton ball launcher!

Experiment Length

30 min


day 9

  • Short pencil or Popsicle stick

  • Two thin rubber bands

  • Two empty toilet paper tubes or one empty paper towel tube cut in half

  • tape

  • Scissors

  • Cotton balls

  • Ruler

  • Energy: the ability to change things

  • Potential energy: energy that has the possibility of causing change

  • Kinetic energy: energy of motion

  1. Use your scissors to cut one of the toilet paper tubes in half lengthwise.

  2. Squeeze the roll so it becomes narrower, then tape it to hold it in place.

  3. Use your scissors or your hole puncher to make two holes in the skinny tube. Make the holes opposite each other, half an inch away from the end, so you can poke your pencil or popsicle stick all the way through the tube.

  4. Carefully push your pencil or popsicle stick through the holes you just made.

  5. On your second toilet paper tube cut two slits into one end of the tube about one quarter inch long and one half inch apart.

  6. Cut two more slits on the same end of the tube directly across from the first two.

  7. Carefully loop one rubber band through the slits on one side so that it hangs from the cardboard piece in the middle. Put a piece of tape over the slits to reinforce the cardboard tab.

  8. Loop the other rubber band through the slits on the other side of the tube. When you are finished the tube should have a rubber band hanging from each side.

  9. Holding the rubber-band tube so its rubber bands are at the top, slide the narrower tube into the wider one with the pencil end at the bottom.

  10. Carefully loop each rubber band end around the pencil.

  11. Hold your launcher so that the pencil is at the bottom. Place a cotton ball on the top so that it rests inside on the narrower tube.

the science

In this activity you used two types of energy to load and launch your cotton ball. As you drew back the pencil with the cotton ball loaded you were adding potential energy to the system. The farther you pulled back on the pencil, the more potential energy was being stored.


When you released the pencil the energy became kinetic and the cotton ball should have gone flying through the air! The farther you pulled back on your launcher the more potential energy you added to the system—and the more you stored the more kinetic energy should have been released when you shot the cotton ball. As a result, the farther you pulled back on the launcher, the farther the cotton ball should have traveled. 

Taking it further

Try testing if pulling back the launcher for a longer period of time affects how far the cotton ball shoots.

Reading on potential energy

Reading on kinetic energy

Inspired by Scientific American

Special thanks to Honor Pimentel for the Spanish translation

daily challenge

Post your photos and video on social media with #curieusinquarantine or send them to us at for an entry into our raffle!

We will select one lucky kid tomorrow to win a free Curieus swag bag with a Curieus shirt, stickers, and candy. Submit your entry to by 8 pm on Sunday, May 24th!

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