Teacher Demo

(information provided by “How Disc Brakes Work” http://auto.howstuffworks.com/disc-brake.htm)

To try and provide some real life examples of how friction applies in real life and occurs in the slow rollers, the teacher may want to give a small lesson on how disc brakes work in a car. As can be seen below in the diagram, the setup is very similar to how the slow roller works, with the exception that in the slow roller the brakes are constantly on.

The analogy is rather simple. In a car, when the person driving pushes the brake pedal down, fluid moves and pushes the piston against the break pads. The brake pads then squeeze against the rotor, and the friction between the pads and the rotor slow the car down.

In the activity for the children, the pairs of wheels are their brake pads. There is no piston or caliper helping to create friction, but rather the material itself creates the friction constantly as the can (similar to the car wheel/rotor) rolls down the incline.