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Where the Rubber Meets the Road
Task with Student Directions
Contributed by: Kentucky Department of Education (KDE)


TASK: S2 - WHERE THE RUBBER MEETS THE ROAD                             Grade 8
Student Name: _________________
School Name: _________________________ School Code: ________


Write your name, school name, and school code on the lines above. Do not open this packet until the directions tell you to do so. You will have a total of 45 minutes to complete this task. You may use up to 20 minutes to complete the group work on this page.

Your group should have the following materials:

  • three strips of asphalt labeled D, W, and O
  • two blocks with rubber
  • one spring scale
  • one 200-gram container of sand
  • a Data Sheet for each person
  • pencils

Race cars and large trucks have very different tires. The purpose of this activity is to examine differences in the two types of tires and examine the effects of different factors on the amount of force needed to overcome sliding friction, which is similar to what happens when a vehicle tries to stop suddenly. Your group will measure the force needed to overcome inertia and start the blocks moving.

You have been provided with two blocks with rubber surfaces (labeled "hard" and "soft") and with three strips of asphalt. Strip D is dry asphalt, strip W is wet, and strip O is oily. (If strip W or O is dry, tell the facilitator.)

You will test each block twice-alone and then weighted-on the asphalt strips. First you will test both blocks on strip D, then on strip W, and finally on strip O. Each of you must record all the group's data on your own Data Sheet.

  1. Asphalt strip D (dry)

    1. Attach the "hard" block to the spring scale and place it on the correct asphalt strip. Begin pulling the block by pulling gently on the spring scale. Continue pulling until the block has reached the edge of the asphalt strip. Be careful to pull on the spring scale with a continuous, steady force. On your own Data Sheets, record the force required.

    2. Now examine the effect of increased mass on the movement of the block by repeating the procedure. This time, place the 200-gram container of sand on the block. Again, record on your own Data Sheets the force needed to start and keep the block moving.

    3. Repeat steps a and b, using the "soft" block instead of the hard block.

  2. Asphalt strip W. Repeat steps a, b, and c, using the wet asphalt strip.

  3. Asphalt strip O. Repeat steps a, b, and c, using the oily asphalt strip.

Record data from all the steps on your own Data Sheet.

Kentucky Department of Education                       Performance Events 1994-95

Data Sheet

Student Name: _________    School Name: __________   School Code: ________

Hard Block Soft Block
   no weight      weighted      no weight      weighted  
   Strip D (dry asphalt)   

   Strip W (wet asphalt)   

   Strip O (oily asphalt)   

When your group has completed steps 1 through 3 and you have recorded all the data on this page, one member of the group should tell the facilitator that your group has finished its work. Then do the individual work. Remember that you must work alone on those pages. You may not discuss the questions or share information.

Kentucky Department of Education                       1994-95 Performance Events

Individual Activity

4. What were the differences, both measured and observed, between the two types of rubber?


5. Produce a graph that represents the relationship between the force and the mass (the pull on the spring vs. the load on the rubber).

6. In what ways would the information you've collected affect your decision when selecting tires for a school bus?


7. Variables such as those you tested (water and oil residue) affect stopping distances. Identify another variable that could affect stopping distance and design an experiment you could conduct to test this variable.


8. What are some of the merits as well as some of the limitations of using the model in this experiment (asphalt strips, blocks, etc.) to represent automobile tires? Support your conclusions.


Kentucky Department of Education                       Performance Events 1994-95


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