Materials (per student group)

• 1 toy dump truck
• 1 pint milk or juice container
• 4 large plastic drinking straws
• 2 coffee stirrers (round)
• 1 toilet paper tube
• 8 cardboard circles (4 cm in diameter)
• 1 push pin
• 1 sharpened pencil
• scissors
• masking tape
• 1 lump of clay
• 1 strip of posterboard (30cm x 45cm)
• Activity Sheet

Leading the Activity
Involve the students in a review discussion of how the wheel and axle interact. Encourage students to observe the wheel and axle construction on the toy dump truck. Challenge student groups to build two race cars and predict which will travel the greatest distance. Invite student groups to test the race cars and record results.

Procedure

1. Place the pint carton on its side.
2. Measure to find the middle of the carton.
3. Draw a line around the middle of the carton (parallel to the desk).
4. Carefully cut the carton along the line, dividing it in half.
5. Place one half of the carton on the desk with the open side up.
6. Measure and mark the both long sides of the carton at the corners 1 cm up from the bottom and 1 cm in from the corner. Construct Type 1
7. Carefully use a push pin to make the four holes and enlarge the holes to the size of the stirrer with a sharpened pencil.
8. Push the stirrers through the holes at the front and the back of the carton.
9. Carefully use the push pin and pencil top make holes in the center of each of the cardboard circles.
10. Measure and cut the paper tube into 8 circles, 1 cm wide.
11. Place the cardboard circle in the center of the paper tube circle and secure with tape. (Put 4 of these wheels aside.
12. Attach 4 wheels to the stirrer axles. (If the wheels do not fit tightly, add a small bit of clay to the ends of the axles.
13. Use the books and posterboard to construct a ramp 20 cm in height.
14. Tape the bottom of the ramp to the desk or floor with tape.
15. Mark a finish line with masking tape 2 meters from the bottom of the ramp.
16. Position your racer at the top of the ramp with the back wheels even with the ramp edge.
17. Release the racer; measure and record the distance traveled in centimeters. (Be careful not to push the racer!)
18. Do 2 more trials. Measure and record the data for each trial. Construct Type 2
19. Cut 2 large drinking straws 2 cm shorter than the stirrers.
20. Prepare the holes on the second racer by repeating steps 5 and 6.
21. Carefully use a push pin to make the four holes and enlarge the holes to the size of the straw with a sharpened pencil.
22. Push the straws through the holes and tape in place.
23. Push the stirrer axles through the straws and attach the wheels.
24. Predict how the Type 2 Race Car will perform compared to Type 1.
25. Test this racer on the ramp; do 3 trials; measure and record the results. (Be careful not to push the racer!)
26. Discuss and record your conclusions.

Teacher Background Information
An axle that rotates freely reduces the friction between the axle and the frame of the race car. Type 2, therefore, should out perform Type 1 because the stirrer axle rotates inside the larger straw. The straw prevents the axle from rubbing directly against the car body.

Range of Results
Careful measurement and placement of the holes for the axle is necessary for the alignment of the race car axles and wheels. Remind students to practice safe handling of the push pins and the sharp pencils as they puncture the carton and enlarge the holes.