Explorit Science Center was recently featured on “Good Day Sacramento,” where several of our summer science campers demonstrated the difference between potential and kinetic energy by exploding a watermelon with rubber bands. You can join in the fun at home, too, with your own melon explosion.
You will need a watermelon, 300 to 400 rubber bands, some goggles or protective eyewear, and about a half an hour. Set this activity up outside where it will be easier to clean up. This will get messy!
The rubber bands are much easier to slip over the melon with another person, so be sure to get a helper. Put on your goggles to protect your eyes before starting, because you never know when it’s going to blow.
Set your melon on a table or other stable surface and one at a time start slipping rubber bands around it. You want to make a big belt of rubber bands around the melon’s middle, so just keep stacking them on top of each other.
After a few minutes of applying rubber bands, pause and take a look at your melon. Is it still the same shape? You may start to see the top and bottom of the melon bulge out around the rubber bands. Why do you think that’s happening?
You have to stretch the rubber bands out to get them around the melon. But once they’re in place, they start to contract, squeezing the melon. All that pressure from the outside is forcing the inside of the watermelon to find someplace else to go, so it’s starting to bulge.
Rubber bands are a great example of potential energy. Potential energy is energy that is stored up, not being used, just waiting to be unleashed. Think about when you stretch a rubber band, then let go and it snaps back. It’s using up its potential energy.
When potential energy is used up, it becomes kinetic energy — energy in motion. So right now, all those rubber bands around the watermelon are stretched out and full of potential energy, ready to snap back. But what will happen to the melon in their way?
Keep adding rubber bands and eventually the strength of the rubber bands’ potential energy will put enough force on the watermelon to squeeze the top and bottom of the melon apart. The rubber bands will cut through the melon and contract. What do you expect the melon to do?
Once your melon explodes, the rubber bands will have snapped back and used up their potential energy for now. But you can always stretch them out again!
Explorit’s coming events:
* Explorit’s “Beautiful World: Science and Art” exhibition is open to the public every Wednesday, Saturday and Sunday from 1 to 5 p.m. and every Friday from 3 to 6 p.m. Admission is $5 per person; Explorit members, teachers and children 2 and under are free.
* Interested in membership? Think your Explorit membership may have lapsed? Call Explorit at 530-756-0191 to check or sign up.
* Birthday parties are back at Explorit! Call 530-756-0191 for more information or to book your party.
* Don’t miss Explorit’s summer field trip to the Discovery Museum’s Challenger Center on Wednesday 6 for fifth-, sixth- and seventh-grade students. Search “Explorit” on brownpapertickets.com.
* Save the date: Sunday, Sept. 7, for Explorit’s “Final Blast Festival and Chemistry Show.” This event celebrates the end of our Summer Science Camp season and is a fun way to start the new school year.