PT2.4 - Testing of Car

Mass of Car 313.3 Grams
Wheel Diameter 12cm(Back)
Axel Diameter 2-4mm
Length of string 45cm
Length of lever extension 15cm
Overall length 3cm
Overall Width 20cm
Overall Height 12cm

Final Car

Run Number Test Run 1 Test Run 2 Test Run 3
Total time of test run/s 15 8 12
Total Distance of test run/m 4 4 6
Observation 1:
Was the car in a steady and stable motion throughout
yes No, the car was going straight until the fishing line got caught on the wheel, probably due to the balloon rubber protruding out Yes
Observation 2:
Was the car moving in a straight line mostly?
No, the car went in a semi-circle before coming to a stop at the boundary Yes, until it came to a halt No, it tilted towards the left quite a bit
Observation 3:
Did lever and string operate smoothly as well as expected?
Yes No, as mentioned in Observation 1, The line got caught on the wheel and it came to a halt Yes
State 1 area for modification. Use a glue gun to straighten the wheels so it does not sway toward the left. Glue the balloon onto the CDs properly. Cut of any access bits of rubber from the wheel On the final run starts the car at an angle facing the right side to counter balance the turning nature of the car
State rationale(s) for above-proposed modification By straightening the wheels, it allows a straighter path By cutting off excess rubber from the wheel and sticking the rest onto the surface of the wheel, it reduces the chance for the string to get caught on the wheel As the final score is measured by displacement and not distance

From the graph above, it shows that the maximum distance of 6m was met at around 13.25s. 
Therefore, we can calculate the score of our car.
Total score =70-10p+2d-2(t-1)
Where p= Number of rule Violations
d= Every 0.5 meters travelled(Capped at 7.5 meters)  
t=Run time in seconds(At least 1 second)

Therefore, our car scored

The car traveled roughly 6 meters.
Therefore the average Velocity of the car 
=Total Displacement/Total Time
=6m/(13.25 s -7.2 s)
=0.992 m/s^2(3.S.F)

3.2 Post testing "Discussion"

 1. Using your data table from 3.1 calculate the average velocity for your mousetrap car during the best run in the final assessment.
2. Which part of your mousetrap car design worked best? Explain your answer.
3. If you had more time to work on your mousetrap car,  state and explain how you will improve/modify the current design?

1.This is the derived Velocity time graph of the graph. To find the average velocity of the car, we need to find the Total displacement traveled and divide it by the total time, however, this is a best-fit line graph,  so it won't be all that accurate.
2. We believe that the back wheels played a big part in the distance of the car. The back wheels were made by glueing 3 CDs together. Balloons were then cut and pasted onto the CDs to increase traction. We chose balloons as they are made from rubber and rubber is known to increase friction on rough surfaces such as asphalt. 
3. If we had more time to work on the project, we would use smaller wheels, shorter lever arm and possibly ball bearings.  
We would have stuck ball bearings onto the wooden body of the car before inserting the axle of the wheel. This is because wood has more surface friction than ball bearings. This would allow the axle to spin more even after the string has fully unwound. 

Also, by using smaller wheels and a shorter arm, we would increase the torque acting on the axle of the car, increasing the revelations per minute(RPM) and allowing the car to go a lot faster.

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