As students progress through elementary and middle school, their science curriculum tends to double back, repeat and slowly build on the same topics. This means, many activities can be used with a wide range of student age-groups. Such is the case for this force and motion lab, which I've seen bring out the inner race-car-lover in both 2nd-graders and 6th-graders.
Using just a few basic materials, students build tracks and conduct race car experiments to test the effects of increasing the tracks' angle of incline and then the tracks' surface texture on the speed of the cars. We used three of the same toy cars from the dollar store, cardboard boxes, scissors, tape and a ruler. Students will also need something to prop up the tracks. In a classroom, stacks of identical textbooks are an obvious choice. If you're conducting this experiment at home, try stacked cereal boxes, DVDs or magazines.
After making their hypotheses about the outcome of the races, students should cut three equal tracks from cardboard. Ours were 1 1/2 feet x 4 inches. Then attach the tracks to the three stacks of different heights using a small piece of tape. Line the cars up at the starting line, and observe which car finishes first, second and third. Repeat this test several times, and then determine the average speeds for each track.
In my class, four groups of students conducted races simultaneously, so the different colors of the tracks above are just two different pieces of cardboard.
After the test, discuss or have students write about the outcome of the races. Were their hypotheses correct? Did the slope of the tracks affect the speed of the cars?
When that's done, save all of your tracks, cars and stack-making materials for experiment number two: How does the texture of the tracks affect the speed of the cars? This time, you will also need two texture-y materials to cover the existing tracks. We left one track alone, covered the second with aluminum foil and the third with snowy-white felt. The foil was easy to attach with transparent tape. The felt had to be stapled around the edges. Once students predict the outcome of this test, they should attach the three different tracks to stacks of equal height.
Race the cars several times, making sure to record which order the cars finish each time. Then find the average standings for each of the three tracks. After collecting the data, let students reflect on the effect of the tracks' textures on the outcomes of the races. Were their hypotheses correct? How did friction affect the cars' racing times?