1. The Rough and the Smooth
Andrew Rechenberg
Holy Sepulcher School
Grade 8

2. Investigation Question
Does the roughness of a road affect the speed of a car?
I will set up a matchbox car track with a ramp for the car to go down. I will place various grits of sandpaper for a 300 cm stretch of the track. I will measure the time it takes a car to travel over those various grits of sandpaper.

3. Interest
Every time we return from vacation in the summer, we always drive into construction zones as soon as we come into Pennsylvania! I have always wondered why construction zones and other similar areas have lower speed limits than most roads.

4. Research There are many different types of road conditions.
I. Does the roughness of a road affect the speed of a car?
There are many different types of road conditions.
The biggest force opposing a car’s movement is friction.
Sandpaper is paper that has various sizes of particles on it.
Gravity is a force that attracts different masses together.

5. Various Road Conditions

6. Rolling Friction

7. Average Diameter of Particle (um)
Grit Size
Grit Level
Common Name
Average Diameter of Particle (um)
P60
Course
269
P100
Medium
162
P150
Fine
100
P180 82
P220
Very Fine 68
P320
Extra Fine
46.2

8. Other Types of Road Conditions

9. Other Road Conditions

10. Hypothesis
I think that the smoother the road the faster the car will go. The rougher the road the slower the car will go.
The smoother sandpaper will produce less friction on the car allowing it to go faster. The rougher sandpaper will produce greater friction on the car allowing causing it to go slower.

11. Materials A matchbox car 10 pieces of Matchbox track A meter stick
Scissors
Wooden board
Different levels of sandpaper: P60, P100, P150, P180, P220, P320
Tape
Stopwatch

12. Procedure Gather all your materials.
Cut the sandpaper to fit into the matchbox track.
Set up the matchbox track with a wooden board as a ramp.
Secure the board to the table so it doesn’t slide.
Draw a line on the matchbox track near the top of the ramp for the car’s starting point.
Mark a beginning line for starting the stopwatch near the bottom of the ramp and an ending line for stopping the stopwatch that’s 300 cm down the track.

13. Procedure Gather all your materials.
Cut the sandpaper to fit into the matchbox track.
Set up the matchbox track with a wooden board as a ramp.
Release your matchbox car from the starting position and record the time it takes to travel the 300 cm.
Repeat step 7 nine more times.
Secure the board to the table so it doesn’t slide.
Draw a line on the matchbox track near the top of the ramp for the car’s starting point.
Layer the P60 grit sandpaper like shingles on the 300 cm stretch of track. Use tape to secure the sandpaper to the track. Repeat steps 7 and 8.
Repeat steps 9 and 10 for remaining grits of sandpaper.
Repeat steps 9 and 10 for remaining grits of sandpaper.

14. Experimental Set Up

15. Layered Sandpaper Road

16. Procedure
Release your matchbox car from the starting position and record the time it takes to travel the 300 cm.
Repeat step 7 nine more times.
Layer the P60 grit sandpaper like shingles on the 300 cm stretch of track. Use tape to secure the sandpaper to the track.
Repeat steps 7 and 8.
Repeat steps 9 and 10 for remaining grits of sandpaper.
Clean up the materials.

17. Variables, Constants, & the Control
Independent Variable: The different grits of sandpaper: P60, P100, P150, P180, P220, P320, and no sandpaper.
Dependent Variable: Time the car took to travel the 300 cm stretch of track.
Constants: The track, car, distance and angle of the ramp, the stopwatch, and environment.
The Control: The track with no sandpaper.