# Control: the Car Without a Change in the Wheel Size

Experiment 1

Question:

What is the effect of the wheel size on the time it takes the car to travel two meters?

Hypothesis:

If we decrease the size of the wheels, then speed will increase because they bump into the cart less and won’t slow it down.

Groups:

Experimental: Wheel size

Control: The car without a change in the wheel size

Constants:

• Distance car must travel
• Angle of the board
• The material inside the bottle
• Materials:
• 4 large wheels (wood, 9.5 cm diameter)
• 4 medium wheels (wood, 6.5 cm diameter)
• 4 small wheels (wood, 3.5 cm diameter)
• 1 2-liter soda bottle filled with cotton balls
• 1 base (wood, large enough to fit bottle on top)
• 2 wooden rods
• 1 wooden ramp (1 meter)
• 1 wooden block placed 1 meter away from the end of the ramp
• A clear space at least 2 meters long
• stopwatch

Procedures:

1. Attach small wheels to the rods, then put those on the base
2. Set up the ramp at a 45 degree angle
3. Measure 1 meter away from the end of the ramp, and set the wooden block there
4. Place the car at the top of the ramp with the stopwatch ready
5. Time how long it takes for the car to reach the wooden block
6. Check the safety of the egg
7. Record your data and repeat 5 times
8. Follow steps 1-7 using the medium and small wheels

Data Chart:

Data Chart experiments.docx

Conclusion:

The problem question my group investigated was “What is the effect of wheel size on the time it takes the car to travel two meters?” Our hypothesis stated “If we decrease the size of the wheels, then speed will increase because they bump into the cart less and won't slow it down.” We found that the smaller the wheel was the faster the car travelled. Our hypothesis was valid. According to our data, when the diameter of the wheel was 3.5 centimeters the average time it took to travel the two meters was 0.9 seconds. When the diameter of the wheel was 6.5 centimeters the average time it took to travel the two meters was 0.95 seconds. When the diameter of the wheel was 9.5 centimeters the average time the car took to travel the two meters was 1 second. The data shows an increase in time as the wheel size increased.

Of course, much of the data may have been affected by human error, especially outliers in the data. These may be things such as letting the car go and starting/stopping the stopwatch at different times, a slight change in the board angle, sudden malfunctions with the car, and changes in the surface material. The knowledge gained from this experiment can help us to build a faster car, and have a more controlled environment. In the final design, we can improve the speed and accuracy (how straight the car moves) of the car based on our data.