In Science Class our assignment was to build a car, that is made out of only card board, wooden skewers, duck tape, CDs, and rubber bands. The car would only be allowed to be powered to one rubber band.
This is an image of what the original design looks like, that we were supposed to start out with. The card board is cut out into a 4 by 6 square, with a part cut out in the middle.
The skewer goes in that cut out part and attaches to the wheels by duck tape.
The rubber band connects to the skewer by wrapping around the flap made out of tape in the center. You then wind it backwards. The elastic potential energy is formed by the stretching rubber band, and then is converted into kenetic energy by spinning the wheels and skewer and making it move.
Our original design got 3 1/2 feet.
After we made our first design, and made progress; we changed it up a lot. This is our second design. We got 8 1/2 feet because we changed the rubber band to a thinner and longer one. This wound a lot more, so there was more energy.
This is our third design. Take three: This time we untapped the wheels and re taped them, with less tape but a better structure that spun a lot longer and faster. We also got a rubber band that is a little bit thicker. It was able to wind tighter. We also taped it farther away from the skewer so it stretched more. This brought more elastic potential energy, which then converted to kinetic energy. The distance reached was- 13 1/3 feet.
This is our fourth design. Take Four: This time it did not go as well, we cut the front to make a point. I thought that this would cut through the air easily and catch more speed, it did not. I think that the main reason that it did not work, was that the dick tape was covering the front and slowing it down as it dragged on the floor. Also that the card board is getting really week, and the limbs are bent.
This is our fifth design. We changed it a lot this time. We got a rubber band that is a lot thinner and stretchier. We also reinforced the limbs by adding a lot of duck tape. The tip of the triangle is Alsace taped very precisely so it does not drag and keep it from moving. We also taped multiple layers of tape on the skewer, and put the wheel on it. This helped a lot.
We wound it and we got eight feet, but it went backwards. We later learned that when we wound it, we positioned it in the way that made it go backwards.
This is our sixth design. This time we started over, we put giant rubber bands on the wheels to make a smoother and faster drive, which would have more traction which adds velocity. We also got a new card board and kept it square this time. The wheels are also taped the way they were on the original design. Then we put the skewer in the middle, and had a bigger flap of tape. Then we got a longer, but thicker rubber band and taped it as far back as possible with a layer of tape. We got 14 feet.
This is our seventh design. This time we taped the left limb of the car to reinforce it because it was bending, and weakening. When we did this the stick would stop being interfered and it would stay straight when wound. We also retapped the rubber band a few times because it kept coming off. It was stronger that way. We got 17 feet.
This is our eighth design. This time we changed a lot of the car. We added another skewer, that is being stuck into the back all the way through. We used this to tie the rubber band to it then attach it to a rolled up flap of tape, which makes if go really fast. It makes it go fast because the rubber band is wound a lot more and does not slip out of the holdings of tape anymore. The rubber band was short and thick. We got six feet.
This time we used a different rubber band that was green, thinner, and a lot stretchier, and reinforced the wheels, we got 5 1/2 feet. The tape and the weakness of the flimsy rubber band prevented the car from going really far.
This is our tenth design. This time used a new rubber band, that is a lot stronger, which allows it to have more elastic potential energy. Another thing that we did differently was that we taped the wheels differently, by wrapping the tape on the stick again; which made it go a lot faster and longer. We got 18 feet.
This is our eleventh, and final design. This time we added a lot more layers of tapes on the sticks, so the wheels will be completely connected. We also added a very small flap of tape in the center of the skewer, which the rubber band could hook on to. We got 23 feet.
The second part of the assignment, was to make a video using the video physics app. The video physics app, is an app that records the video of your car moving, and tells you the velocity of the car.
The equation for velocity is change in position/change over time. What I had to do was take the velocity and find the acceleration. After you make the video, the app gives you graphs of the velocity using points on a coordinate plane. You have to use the lowest point and highest point of the velocity and find slope, which is the acceleration.
The acceleration for our car is .56 meters per second.
The video, and diagrams are below.
We positioned the video in that way, so the app could capture the velocity. It was tricky to keep it still, because if we did not, the app would not register.
The graph in the video that I used to ding the acceleration is that one that has the y-axis being: x velocity (m/s), and the x-axis being: Time (s).