From Algebra to Calculus—a Tonka® Toy Does the Trick

This classroom presentation is designed to introduce and interpret the graphical representation of a Tonka® toy truck's forward and backward motion. It can be used to illustrate an application of slope in an algebra class or to introduce the derivative in a calculus class. In the presentation, the teacher moves the Tonka® truck up and down on the chalkboard using chalk to record the motion, asks students questions about the motion, and encourages discussion. The class is asked to pretend that the toy truck has a speedometer. Unlike speedometers in real trucks, this toy speedometer has negative values to represent backward motion, in addmon to its usual positive and zero values. (Speed is the absolute value of velocity. In this situation, the speedometer might better be renamed “velocity-ometer,” but that term would introduce vocabulary unfamiliar to the student.) The presentation leads students to develop a graphical representation of the truck's one-dimensional motion, creates graphs representing constant velocity, leads students to a definition of average velocity, and introduces the concept of instantaneous velocity.