I demonstrated how to make marshmallow catapults on Kare11. Here’s the link. It’s right after the apple mummy demo!
All you need for this experiment are some rubber bands, the plastic ring from the neck of a prescription bottle or the ring from the lid of a plastic milk jug, and a bag of marshmallows. You’ll also need a chair turned upside down to complete your catapult.
Make a chain of rubber bands (you can double it to make it stronger) with the ring in the center. You’ll figure out how to do it if you try, but basically, overlap two rubber bands and pull the bottom one through the one on top and then through itself. Voila!
Secure your catapult to a chair, set up a few targets and watch the elastic energy stored in the rubber bands become the energy of motion when you let go of the marshmallow. It may take some practice, but soon you’ll be a confectionery warrior. Let the marshmallows fly!
The science behind the fun is called TRANSFORMATION OF ENERGY. When you pull the rubber band back, you are doing WORK on the rubber band. How much WORK you do depends how hard you pull on the rubber band (FORCE) and on how far back (the DISTANCE) you pull the rubber band. WORK=FORCE X DISTANCE. The work you do is stored as ELASTIC ENERGY in the rubber bands. When you release the rubber band, the rubber band then does WORK on the marshmallow and the ELASTIC ENERGY is transformed into what is called KINETIC ENERGY (the energy of motion) in the flying marshmallow. When the marshmallow hits something and stops, the KINETIC ENERGY is then transformed into heat, or HEAT ENERGY. In other words, the ENERGY you produce by pulling back on the rubber bands isn’t lost. It’s just transformed from one kind of energy to another.