Experiment: Edible Energy Explosion

Our own Fruit Ninja in Training (Ryan age 6) had a question. Can the force and pressure of a lot of rubber bands wrapped around of the middle of a watermelon really make the watermelon explode?  If so, how many rubber bands would it take to make a watermelon explode?  The guesses ranged from 50-1,000 and we recorded all of the opinions of the children on a piece of paper.

We started our experiment by placing rubber bands around the middle of a watermelon. The kids helped to count the rubber bands as the staff stretched them around the watermelon. We started out placing five rubber bands at a time and were able to practice counting by 5s (to sneak in a little math). After 200 rubber bands were on, we began placing the rubber bands by the 10s. After we hit 500 rubber bands, we had to go back inside and look for more!

As the experiment continued, the watermelon began to ooze bubbles and juice out of where the stem had originally connected the watermelon to the plant. 

Then the watermelon began to crack slowly, and as we placed the 558^th rubber band on the watermelon, it popped! Watermelon showered everywhere like rain and the pieces ranged from baseball sized pieces to mist.

Rubber bands are great examples of potential vs. kinetic energy. When they are stretched, they are full of lots of potential energy (stored energy). When they snap back, this potential energy is converted into kinetic energy (energy in motion), and... boom! Watermelon shower!

The kids really enjoyed this experiment and thanked Ryan for sharing it with the community. Next time we want to try different sized watermelons and see how the watermelon size affects the number of rubber bands needed.

By Erik Wolf