Find and use materials to build a mock up of the machine. So far, my kids have been successful with a LEGO catapult and have discussed how they could use the LEGO NXT (or EV3 which was just released) kit to make another type of machine called a centrifugal- which needs a motor. Of course you can find kits to build catapults and trebuchets (this one is picture above).
An old “standby” I have used often (as a classroom teacher as well) is the shoebox catapult.
For shoebox catapults you’ll need:
pencils (or other strong stick)
egg carton cups
I’d love to tell you more, but then that would take away the opportunity to figure it out! Remember, part of this unit study is just to let your kids explore and discover. Feel free to give pointers or ask questions of your student to help them along. Have the kids plan and make sketches. In my classroom days, I gave a recipe for how to build it and the kids did the work. How much more valuable to design it on their own!
Have fun with the building process- you can choose to give a parameter of time or you can simply let the process run out. Tomorrow, we’ll talk about the physics of siege engines. Join me!