Materials: battery-powered toy moving at constant velocity
-Students measure the average speed WITHOUT using conventional measurement tools (stopwatch, ruler, etc.)
-Students struggle to devise methods, but eventually use a variety of interesting timing devices: pulse, dripping water, cursor blinks, etc.
-Students use markers, shoes, arms, etc. to measure distance.
-Students then report the speed of their object to one another, and no one can understand each other.
-A need is developed for scientific units of measurement.