March 01, 1999 Filed in: Demo Corner

This is a good exercise to use after you’ve done kinematics, dynamics, and energy. We all talk about the kinetic and potential energy of roller coasters and their speeds, and the demonstration will let your students apply their critical thinking skills to this kind of situation. Be sure to have your students examine the setup and predict the outcome,

I give this demo as a quiz, asking students to predict a result (A, B, or C) and write a paragraph defending their choice. I give some points for a correct answer and some more points for a correct, logical argument.

Most students seem to choose B, since it is the shortest distance. Some will choose A, B, and C, or that all will get to the end at the same time. This is perhaps a mixup with the concept that they all have the same speed when they arrive at the end, at whatever time. The correct answer, or course, is A, since it travels its ‘valley’ at a higher speed, more than making up for the fact that it has a little farther to go.

You can build these ramps using curtain rods and plywood (email me for plans), or you can simulate the ramps using