Exploding watermelon- And the Science Behind It
Exploding Watermelon Science
A watermelon isn’t pliable, it has a solid structure with the rind. You can’t deform the melon, remove the rubber bands and have it return to it’s original form.
The rubber bands slowly break the structure of the rind until it can no longer hold together. The rubber bands apply force to the rind forcing it’s shape to change.
You can see how the rubber bands begin to cause the watermelon to deform as they push and squeeze into the rind and the watermelon begins to bulge above and below the rubber bands.
Inside the watermelon there are also changes happening. The water and fruit inside are being forced out of their structure and into areas that don’t have the space for them to be as the force of the rubber bands increases and the movement inside the melon causes it to bulge with the pressure that is being created.
The pressure of the rubber bands causes the pressure inside of the watermelon to increase until the melon splits and the pressure is released with force.
I was helped in understanding this science, by some great answers from some really smart people at Quora.
Potential and Kinetic energy
Potential Energy=stored energy
Potential Energy is in anything that has the possibility to move and have kinetic energy. Potential energy is in everything! A rock can be kicked, thrown or fall; all of which gives it kinetic energy.
Anything that has movement has kinetic energy- ball kicked across a field, leaves blowing in the wind, an object falling from a table, etc.
Some things have more potential energy than others. A rock kicked on the ground has less potential energy than one dropped from the top of a building.
A rubber band has potential energy, but when you stretch it, the rubber band’s potential energy increases.
The rubber bands stretched around a watermelon not only increase the potential energy of the rubber band but also of the watermelon!
If you only put a hundred or so rubber bands on a watermelon it isn’t going to make it explode, but over time it may cause it to split because the force on the rind has changed and continues to do so as the rubber bands want to go back to their original shape.
The more rubber bands added, the more potential energy the watermelon gains in it’s displacement of it’s shape and contents.
small bowl to keep it steady
at least 2 people
1st you need a nice watermelon, not too big, not too small. If it is really big it will be hard to get all of your elastics around it.
I like to have the watermelon up on a table of some sort. It takes a while to get all of the rubber bands around it and if you are having to bend over a lot, your back may hurt by the end. Plus, you don’t want faces down too close to the explosion! It does explode with force and someone could get hurt, so be cautious.
I use a bowl, as you can see, to keep the watermelon still and stable while we work.
You will need at least 2 people to put the elastics around the watermelon. Your fingers get sore and it helps to trade off with someone. (We did this a few years ago and I got blisters on my fingers! Ouch!!!) Wearing some gloves helped, but be careful to not get them stuck when placing rubber bands.
We did approximately 300-400 rubber bands around the watermelon.
It helps to have multiple people helping and taking turns placing the rubber bands. Sometimes they were pulling 2 or 3 around at a time, trying to get them on quicker. This is the “boring” part of the experiment.
Make sure you are keeping the rubber bands together in one area of the watermelon, as much as possible.
It is fun to note the changes. You will begin to notice it bulging above and below the rubber bands.
It will begin to leak. The first time we did this it made kind of a hissing sound before it exploded. We were expecting it this time, but there was no warning, which is why they ended up being so close when it exploded. They didn’t even let the last rubber band go, when it burst open. They did get hit with flying debris but no one got hurt, just surprised!
It is messy business!
Pieces went flying for a long way and are all over the lawn. The rubber bands form a tight ball.
At about 35 seconds in, if you have your sound on, we sound like “Minions”. It is so funny!