My original plan for this meeting was Squishy Circuits. Unfortunately, my test-run didn't work. At all. I'm pretty sure I know what the problem is, but fixing the problem requires ordering some items from Amazon. Since I was basically testing out the circuits the day of our meeting, we had to go with Plan B - a catapult engineering challenge.
Since it was Plan B, I was rushing around quite a bit trying to gather the materials and make some samples, and forgot to do some of the background research I wanted to do - such as, what's the difference between a catapult and a trebuchet. And of course, one of the kids asked that very question. Way back when Steph was taking physics in high school, I actually knew the answer to that question off the top of my head.
In short, a catapult is any mechanical device, that is not a firearm, that is used to throw a projectile a long distance. A slingshot is a type of catapult. A trebuchet is another type of catapult, specifically one that utilizes a counterweight to create tension that when released, propels a load a large distance.
A trebuchet utilizes gravity, while a catapult may utilize tension.
(source: wikipedia, differencebetween.com, differencebetween.net, physics.stashexchange.com)
I did manage to make up two samples for the group, as well as a labsheet showing different designs.
We provided popsicle sticks, plastic spoons, rubber bands, tape, dixie cups, index cards, and a variety of pompoms, spikey balls and ping pong balls to use as projectiles.
They had about 45 minutes to build, test, and modify their designs. Some of the designs used the tension in stretched out rubber bands to build up energy, others utilized a push on the swinging arm to launch.
Our next meeting is in a couple of weeks and I will definitely have figured out the Squishy Circuits problem by then. ;-)