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Pocket Slingshot

The weather is finally starting to cool down and my kids are venturing back out from the comfort of air conditioning back into the outdoors.   The game of choice right now is battling – in all shapes and forms. To avoid too much damage from wacking away at each other with swords (aka sticks), I introduced this slingshot

A traditional slingshot is made with a rubber band and a Y shaped stick, which is often hard to find. This small balloon slingshot fits more easily in your pocket. Add some small wads of paper (or mini marshmallows) and you will be ready for battle anytime and anywhere.

All you need are scissors, a plastic drink bottle and a balloon.

  • Use the scissors to cut the top off of the bottle just below the mouth.
  • Cut off the narrow part of the balloon.
  • Stretch the rest of the balloon over the mouth of the bottle
  • Pull the narrow part of the balloon onto the mouth of the bottle as well. Roll up the smaller piece of balloon so that it holds the larger piece in place.

To shoot, put a small wad of paper or marshmallow ammunition in the balloon. Pull back the balloon and release so that the ammunition shoots out . How far can you shoot? Put out a paper cup or other target to see how accurately you can shoot the slingshot.

How does it work?

This slingshot uses the 1st law of thermodynamics, which states that energy cannot be created or destroyed, only transformed from one type to another. In this case chemical energy in your body is converted to motion energy as your arm pulls back the balloon, which then absorbs that energy as elastic potential energy. Releasing the balloon converts most of the elastic energy to kinetic motion energy (and a tiny bit to heat energy from friction) as the marshmallow flies through the air.

Experiment a bit to make your slingshot better!

What if you use a wide mouth bottle or a narrow mouth bottle? Does the size of the opening affect how far or accurately you can shoot a marshmallow?