PT2.4 - Testing of Car


Testing of Car

Testing & Modifications
Run NumberTest Run 1Test Run 2Test Run 3
Total time of test run / s1.154.73
Total distance of test run / m12.24
Observation 1:
Was the car in steady and stable motion throughout?
YesNoYes
Observation 2:
Was the car moving in a straight line mostly?
YesYesYes
Observation 3:
Did the lever and string operate smoothly as well as expected?
NoNoYes
State 1 area for modificationRebuild the entire car, reducing gear ratio. Coil the string tighterWe could change the mousetrap to a newer one. 
State rationale(s) for the above proposed modification.The gear ratio converts too much torque to speed thus there's too little force to power the car. Hence the only way to achieve 7.5 m is to remove the gears. Coiling the string tighter around the axel prevents the string from tangling and springing the car backwards. The mousetrap travels with a slow speed despite having maximum spring-to-wheel efficiency. The only reason for this is that the spring has been weakened after the numerous testings. 

Test Run 1

Test Run 2

Test Run 3
Final assessment
Mass of mousetrap car250 g
Mass of each wheel45 g
Wheel diameter8.5 cm
Axel diameter0.5 cm
Length of string (from end of lever to axel)29 cm
Length of lever extension15 cm
Overall length29 cm
Overall width15 cm
Overall height8.5 cm

Run NumberTrial 1Trial 2Trial 3
Total time of Run / s5.1--
Total distance of Run / m7.5--
Total score91.8--

We were satisfied with the score of 91.8, thus we only did one trial.
Best Run
Side view
The purpose of the side view is to plot the distance travelled over time so that velocity could be calculated.


Front view
The purpose of the front view is to ensure that the car does not move sideways.


Video analysis


Velocity-Time Graph


Distance-Time Graph


Graph analysis
Velocity-Time Graph

From t=0 to t=1, the car was accelerating at a decreasing acceleration.
From t=1 to t=3, the car was travelling at a constant speed of about 1.85m/s.
From t=3 onwards, the car was decelerating at a decreasing deceleration.

Calculation of Score

The car travelled 7.5 meters in 5.1 seconds. By the formula 70-10p+2d-2(t-1),
our total score = 70-10(0)+2(15)-2((5.1)-1) = 91.8

video_labelhttps://youtu.be/MM84g2XGpCY

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.
1.47m/s

2. Which part of your mousetrap car design worked best? Explain your answer.
The lego speed gearing. It allowed the mousetrap car to efficiently transfer its elastic potential energy into kinetic energy and then it increases that by twice the amount due to the gear ratio which would allow the car to travel faster.

3. If you had more time to work on your mousetrap car, state and explain how you would improve/modify the current design?
I would use lubricant between the wheels and the chassis to reduce the loss of energy due to friction. We would also have used lighter materials like balsa wood rather than lego as lego is quite heavy and the wheels at the front could be thinner and lighter so the car could travel further

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