The more stopwatches and cars the better. Many students could be involved by having them act as official timers. Actually, this is preferred since mistakes are very common when it comes to working stopwatches. The stopwatches might have a few features which cause re-setting confusion; so, if five timers are employed, a couple could drop out and youíd still have three good readings.
No two cars will operate at the same speed. For fun, itís best to have a good variety of cars, ranging from big-wheel tracksters to little roadsters. Itís also a good idea to have extra batteries around. These kinds of cars will run at surprisingly constant rates provided, of course, the surface is level.
These experiments must always begin with teams of students determining the velocity (speed, actually, since direction will always be forward) of each car. To do this, they should mark off a pretty good length (30 feet or more), then time the car over the stretch of distance. It would be very unusual for these kind of cars to travel a straight line over such a distance, so it a good idea to use a long stick (yard or meter sticks or longer) to poke the car along its side to keep it in line (with practice, this will work just fine). This determination of each carís velocity must always be done because no car will have the same speed over different battery ages and different surfaces. There are a myriad of experiments that can be performed once these speeds are known. At the very least, the students could be asked to determine how far a particular car would travel in a prescribed number of seconds; or, how long it would take a car to travel a prescribed distance.Excellent activities include such things as:
Clearly, mathematical solutions for all of these activities can be matched against the empirical time and distance results when the actual experiments are performed.