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COPYRIGHTED MATERIAL some of the energy that would otherwise go into moving the car forward. Similarly, the bumps on the mesh shelf liner shake the car, which also diverts energy from moving the car forward. This is why the cars on these two tracks move more slowly. Mathematics Content This activity encourages measurement of both speed and distance. While younger children will judge speed and acceleration based on visual perception, older children can clap at regular intervals to mea- sure the time a car takes to reach the bottom of each track. (In this case, they will need to race the cars one at a time.) A metronome, which produces sounds and light flashes at regular intervals for musicians to follow, is even better to use. These devices are not ex- pensive and can be used in a variety of activities. The gridlines along the floor help children begin to quan- tify measurements of distance. Children can also link together manipulative materials, such as snap blocks, to measure distance. This helps children realize that measurement involves use of a designated item as a unit, and the number of units used is the distance. Children will likely want to discuss the order of finish of the cars, which leads to the learning and application of ordinal numbers—fi rst, second, third, and fourth. They may even want to record the order of finish on a score sheet. Connections to Technology and Engineering Use of a digital video camera to preserve some of the ramp experiments allows children to review the re- sults and the teacher to lead discussions with groups of children. As children watch the cars move down the various tracks, they can together clap and count pulses to determine speed. Children can also com- municate about the experiments and share their infer- ences regarding what affects the speed of the cars. Understanding how the surface of roads affects speed is important to civil engineers. Sometimes curves on a steep road have ridges to help prevent vehicles from going too fast. Teachers can intro- duce these concepts through their discussions with children. Comments and Questions to Support Inquiry • Does the car on the wood ramp always get to the bottom first? Why do you think that happens? • This time let’s watch for the car that comes in third place. • Can you predict which car will go the farthest? • Does the fastest car always go the farthest? • Does the slowest car always go the shortest distance? COPYRIGHTED MATERIAL ST E M lE aR n I ng c E n T E R S 23