Invent-a-Wheel develops energy concepts through students' attempts to get something to slide, and eventually, roll down a ramp.The key concepts, which are largely implicit, are gravitational energy and its enemy, friction.
Students begin by exploring ways to get an object to move, perhaps by pushing, pulling or blowing on it. The next challenge is to find a way to get it to move by itself – without touching it. An obvious solution is to make a ramp. In Lesson 3, students use small cardboard rectangles as sleds, and investigate how the height of a ramp affects whether a sled will go down. The following lesson focuses on how different surfaces affect sliding. Children's focus then shifts to how to redesign their sleds: how can the sled be improved so it slides better? Next, students improve the “slipperiness” of a sled by putting rollers underneath. However, these rollers separate easily from the sled, and do not follow it beyond the bottom of the ramp. To solve this problem, students attach the rollers to the sled – thereby inventing the wheel! A sled with wheels is a car. They test their cars, they draw and write about their cars and they create a How-to Books explaining how to make them.