The Rough and the Smooth

Andrew RechenbergHoly Sepulcher School

Grade 8

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.

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.

Research

I. Does the roughness of a road affect the speed of a car?

II. There are many different types of road conditions.

III. The biggest force opposing a car’s movement is friction.

IV. Sandpaper is paper that has various sizes of particles on it.

V. Gravity is a force that attracts different masses together.

Various Road Conditions

Rolling Friction

Grit Size

Grit Level Common NameAverage Diameter of

Particle (um)

P60 Course 269

P100 Medium 162

P150 Fine 100

P180 Fine 82

P220 Very Fine 68

P320 Extra Fine 46.2

Other Types of Road Conditions

Other Road Conditions

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.

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

Procedure

1. Gather all your materials.2. Cut the sandpaper to fit into the matchbox track.3. Set up the matchbox track with a wooden board as a ramp.4. Secure the board to the table so it doesn’t slide. 5. Draw a line on the matchbox track near the top of the ramp

for the car’s starting point. 6. 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.

Procedure

Gather all your materials.

Secure the board to the table so it doesn’t slide.

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.

Draw a line on the matchbox track near the top of the ramp for the car’s starting point.

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.

Set up the matchbox track with a wooden board as a ramp.

Cut the sandpaper to fit into the matchbox track.

Repeat steps 9 and 10 for remaining grits of sandpaper.

Experimental Set Up

Layered Sandpaper Road

Procedure

7. Release your matchbox car from the starting position and record the time it takes to travel the 300 cm.

8. Repeat step 7 nine more times.9. Layer the P60 grit sandpaper like shingles on the 300 cm

stretch of track. Use tape to secure the sandpaper to the track.

10. Repeat steps 7 and 8.11. Repeat steps 9 and 10 for remaining grits of sandpaper. 12. Clean up the materials.

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.