Pages

Rat rod vs Lambor

Tuesday, June 7, 2016

Better Safe Than Sorry

What was the challenge?

The main idea of this project was to use the physics concepts that we have learned in class to design and understand the safety mechanisms in cars. Such as, brakes, seat belts, air bags, frontal crumple zones or by simply using vehicle mass. To show our understanding of these concepts, we were told to build a safe car by incorporating these safety mechanisms, by using some of the materials provided (spaghetti, tape, cotton, clay, dough, aluminium foil, a passenger compartment, etc) and by following guidelines that prohibits you from using certain material in certain parts of the car. The problem that we were faced with here is that there would be a raw egg inside the car to act like a passenger. And when designing the car, students were only allowed to use one safety mechanism in their vehicle.The goal of this was to protect the egg from breaking after traveling down an approximately a ramp of 48 centimeters in altitude.


How did you choose to approach the challenge?

To deal with this challenge, my partner and I decided to create a frontal crumple zone, in other words a bumper, that will absorb the impact of the crash effectively,and stop the forces from impacting the egg itself. We did this by using certain amounts of materials such as cardboard, tape, plastic box as our passenger compartment, and scissors. We tried to design the car as simple as possible so that the mass of the car will be lighter, therefore the car won't be able to gain much speed while it speeds down the ramp.





Our design was like a spring inspired bumper as we folded the cardboard in order for it to look and act like  spring, so in the end, our design practically looked like a car with a gigantic spring for its bumper. The reason why we designed the bumper as a spring like shape was because we thought that as the impact of the force will start pressing the spring, the spring will shrink and start reducing the amount of force from the crash that will reach the egg as it takes a certain amount of force to pressurize the spring. Thus, our car was basically an egg and a plastic box with a huge spring in front of it. 


Here is our final design:



How did you test and evaluate your design?

To test and evaluate whether our design would be a successful in protecting the egg or not, we followed the procedures given to us. It told us to use a track that fit the car's wheels and to test the crash with a ramp with the altitude of 48 cms. For each trial, we timed how long it took the car to finally crash into the wall and how long the car traveled, in order to calculate its velocity. We also recorded if there was any harm done to the egg or not. Here is the following raw data we collected:

Car's mass: 186.2 g for the plastic box and material and 1000 g for the metal car. Therefore the total mass of the car was 1186.2 g.


Trial Number
Time (s)
Distance (m)
Success? (yes or no)
1
0.8
1.21
Yes
2
0.9
1.21
Yes
3
0.8
1.21
Yes


Trial
Speed (m/s)
1
1.21/0.8 = 1.51
2
1.21/0.9 = 1.31
3
1.21/0.8 = 1.51


From our results, we evaluated our design of the car to be fairly successful, as we had a 100% success rate in saving the egg from the crash. And as the egg did not break even once from the all the trials, we were so confident that we decided to test the car from a steeper angle to test if whether the procedure or materials that they have provided for us were actually valid for test like this. Here is a video below that will show you that the egg still didn't break even after we have tried the test from a steeper higher ramp.




In this trial, the egg again does not seem to break. But now, the real question that we have to start asking at this point is " Is it our design that is saving the egg or is the plastic box that we used strong enough to protect the egg?". After we have asked other groups about their results, almost of them said that their eggs didn't break. Therefore, I think that the passenger compartment of the car itself is enough to be able to protect the egg from cracking from a crash. So, something that I would want to change in our procedure is to make the car use a less sturdier passenger compartment because this would help conduct more valid tests as we would be able to test the full potential of our designs. Another suggestion that I want to make for the procedure is to lengthen the length of the track as the longer the track is, the more force and speed the car will be able to gain. In addition, they would supposedly be traveling at a higher speed, meaning a stronger collision that could potentially damage the egg if the design wasn't very well thought of. In conclusion, I believe that our design for our car was fairly successful, however as the passenger compartment of the car was actually protecting the egg, the effectiveness of our design couldn't be tested in a reliable way.