Who says physics can't be fun? Science isn’t ho hum anymore when it involves building a catapult to teach your child about projectile motion and potential energy. Help your fifth grader build a marshmallow catapult from an ordinary shoe box and other easy-to-find materials around the home. This explosive—albeit yummy—project can be constructed indoors, so save it for a rainy winter afternoon!
What You Do:
- Help your child cut out one end of the shoe box, leaving a one-inch strip across the bottom.
- Starting from that end, have your child mark a point one inch from the top and 2 ½ inches from the back of the box on one of the wide ends. Help your child use a hole punch or craft knife to punch a hole and enlarge it to the diameter of a pencil.
- Repeat step 2 on the other wide side of the box. Insert a pencil through the holes, and help your child use a knife to poke a hole where the end of the pencil meets the bottom of the box.
- Ask your child to use the electrical tape to fasten the spoon handle to the second pencil and cross this pencil to the first pencil, as shown in the picture.
- Help thread the rubber band through the hole on the bottom of the box, putting the third pencil through the loop beneath the box to keep the rubber band from slipping through the hole. Inside the box, loop the rubber band over the end of the second pencil.
Catapults similar to this model were once used to launched rocks over castle walls. This one is perfect for flinging marshmallows at blocks or other light-weight targets. As your child pulls the spoon back, the rubber band stretches, storing potential energy. When released, the energy transfers to the marshmallow in the form of kinetic energy. Ready, aim, fire!