Have students work in groups of three or four to complete this experiment. Each group of students needs a piece of press board, blocks to prop the board to make an inclined plane, a stop watch, paper for recording results, poster board for creating a graph and a toy car.
Give each group glue, scissors, aluminum foil, felt and sandpaper. Students will cut 4-inch wide strips of each material. Students will use the strips to make four "lanes" on the inclined plane or "ramp." One lane will be aluminum foil, one sandpaper, one felt and one uncovered board. Have the students prop the board with blocks behind it at about a 45-degree angle.
Before beginning the experiment, each group should develop hypothesis statements concerning which material they believe will have the most friction and which will have the least. One student in the group will hold the toy car at the top of the first lane. He will let go of the car, allowing it to travel to the bottom of the ramp. A second student will use the stopwatch to time how quickly the car travels to the bottom of the plane. Have the students repeat this process five times. A third student should record the times and calculate the average of the five trials. Repeat the entire process for the other three lanes.
The velocity of an object is equal to the distance divided by the amount of time. Students should measure the distance from the top to the bottom of the ramp in centimeters. As a group, the students should calculate the velocity by dividing the average distance traveled by the cars on each lane by the average amount of time taken to travel that distance. For example, if the ramp is 21 centimeters long and the car takes 3 seconds to travel the distance, students would divide 21 by 3 to determine the velocity. Therefore, the velocity would be 7 centimeters per second.
Once the students have calculated the average velocity for each lane, they need to create a bar graph to show the difference between the velocities of each lane. This indicates which material has the most or least friction. The slower the average velocity, the more friction is involved. Once the graph is made, students should compare their results to their original hypothesis statements. Each group should report whether their hypotheses were confirmed or refuted. The graph and recorded results should be displayed to show the team's work.