The Mouse Has Been Trapped

      "Oh yeah, I can build this mousetrap car with no problem. It will be super easy." These were the thoughts going through my head when I first heard the words mousetrap car project. But after countless hours of work, some blood, some sweat, and many tears I realized I had had not idea what I was getting myself into with this project. However, Margaret Anne and I were eventually successful and the feeling of triumph payed off for all the failure we had endured.

       Our initial plan was to use sewing bobbins for our tires. If you don't know what a bobbin is, it is fairly small. For axels, we used paper clips which did not stay on our car very well. Our lever arm was a piece of plastic that came from one of my hangers that I willingly donated for the cause. This plan failed.....badly. The paper clips constantly fell off no mater how much tape or hot glue we put on and the bobbins were just having problems. The only thing that was a success was the plastic lever arm. With one design out the window, we decided to make a new car with CD's for the back wheels with a piece of a clip attached to the mouse trap itself. Here, we finally started to see some movement. However, this movement was not enough to spark hope in our hearts. Accordingly, we went back to the drawing board. For our next car, we used pencils and lots of hot glue and four CD's. As time went on, we kept getting more and more frustrated. With the final failure of this car, we parted ways in tears. I took the dreaded mouse trap with me, and worked on it till two in the morning, fixing it on the ceramic floors of the bathroom. This ended with a distress call to my mother and many tears. In exhaustion, I decided to end my long day and go to bed. 

         Waking up was easily the hardest thing I had to do that Monday morning. Margaret Anne and I solemnly arrived to conference period in complete frustration. The car was not working no matter the advice we got from Ms. Lawrence, UNCA engineering students, or fellow classmates. We kept trying the car, but with little prevail. Eventually, I left that night with the mouse car in hand, determined to make some progress. For our final design I wrapped tape on two pieces of wire, and then attached the CDs from there so as to keep them stable. We then used screw hooks that attached to our mouse trap (we were able to procure a new one since the previous one was completely covered and glue and not to mention broken). We did not put anything over the CDs at first to see if the lack of friction would make the car go any faster. This actually just made the car turn and move in crazy directions. We then put balloons on the front wheels. We attached the string to the car wound it up, but the car was still not moving five meters. 

        That afternoon, Margaret Anne and I took turns working on the car. She worked on it during lunch and I worked on it during her rehearsal. I tried to modify various aspects to the car, and got it within inches of the finish line. The car seemed to have an equal hatred of me as I had of it. It kept turning in mysterious ways and sometimes wouldn't even go at all. With little hope left, I tried the car one last time and to my great happiness it finally crossed the green finish line! I tried it again to make sure it was really working and....it didn't work. I literally crawled on the floor in tears. Then, I went back in the room, straightened out the wheels and it worked again. Even though I was skeptical, I knew I needed to test the car out one last time, and just like before it did not cross that finish line. When looking at the design of our car, I realized that a piece of hot glue was interfering with our lever arm causing the car to curve in a peculiar way. With this in mind, I removed the glue, and tried the new and improved car. It worked! And with that, I left the physic's room with my head held high.
          Margaret Anne and I encountered various issues in our mouse trap car. For one, our initial wheels were not big enough to propel the car anywhere; they practically weren't able to touch the ground. Also, our string kept getting tangled so we constantly had to reduce the amount of string we had. However, we sometimes had too little string and thus had to add more one. Our lever arm was constantly changing. We tried to make it longer by hot gluing wire to the end of it, but this just weighed the car down. Eventually we prevailed with just the long plastic piece of my well used hanger. Another problem we had was keeping the wheels straight. The CDs constantly wanted to curve which was just not acceptable. We tried to add hot glue to the edge of the hook so as to keep the wheels and the mouse trap in place. However this is how we ran into trouble with the car curving. Once we removed one piece of glue, the car worked and we were the happiest people in the world.
          If I could do this project in the future, I would try to make my mousetrap car even more lightweight to increase the speed of our vehicle. Our car ended up taking seven seconds to cross the five meter mark, but I was so happy that it even made the five meters I didn't care about the time. Next time, I would know how to make our car work, and stabilize the wheels more as wheel. Finally, we had about an 18 inch lever arm, which is a reasonable size. To increase our force, I would increase the distance of the lever arm, but I would try to do this in such a way that the mass would not increase.
          Looking at the Physics applied in this project, we can talk about Newton's 1st, 2nd, and 3rd law. We know that the first law is the desire for objects to either stay in a state of rest or continue moving unless stopped by an outside force.; this is called inertia. Once our mousetrap car started moving, it wanted to keep moving. However, sometimes our lever arm would hit the ground, and this force would cause the car to stop moving. It was times like this that I hated inertia.... a lot. The next law we learned about was Newton's 2nd law which says that acceleration is directly proportional to the force and indirectly proportional to the mass. Therefore, if we had a great force, than we would have a great acceleration. However, if we had a large mass, we would have a small acceleration. Finally, we can apply Newton's third law which says that every action has an equal and opposite reaction. To make our wheels move, we had the string pull on the wheels. If the string pulls on the wheels, the wheels pull on the string and therefore cause movement.
         Friction was a big contributor to our mousetrap car. There are two kinds of friction, kinetic friction and static friction. Kinetic friction deals with two things rubbing together, just like the axel and the wheel. Static friction is the force that opposes a stationary object when something is attempting to move it. We had to consider these frictions with both our wheel and axel, and wheel and the floor. Because we used CDs for wheels, the ends were very slick and the car went out of control. Once we put rubber from a balloon on the front wheels, the car was much more stable and moved in a somewhat straight path. For the wheels and axels, we needed a material that would move but would also cause friction. We used metal rods for axels, and then attached the wheels to the axels by using a large amount of tape. This provided just the right amount of friction we needed.
       Thinking about the wheels we were going to use was hard. We initially thought we wanted small wheels in the front and bigger wheels in the back because then the back wheels would have to go faster because they were covering a greater distance over the same period of time that the small front wheels were. Our bobbin wheels were failures, and in the end we just decided to use 4 CDs. This was actually the best plan because the wheels would cover a greater distance.
       The conservation of energy was ever present in our mousetrap car. We know this law states that energy can neither be created nor destroyed. Therefore, the energy that was put into this car will come out of this car. Before the car was released, the car will have the largest amount of potential energy. Just before the car stops moving, it will have the greatest kinetic energy of the whole experiment. Some of the energy might be turned into heat, but this does not contradict the law of conservation of energy.
        Our lever arm was about 18 inches long. The length of the lever arm directly effects the amount of torque an object has, which is how much an object rotates. The longer the lever arm is, the greater the torque will be. Torque is equal to force multiplied by the lever arm. Because the lever arm was longer, it increased the torque of our car, which was to our advantage. Also, the longer lever arm resulted in a greater potential energy right before the car was released because the spring will have more force on it causing it to store more energy.
         Rotational inertia, rotational velocity, and tangential velocity were also key elements to think about when creating our mouse trap car. If we multiply the rotational inertia and the rotational velocity together, they will equal the angular momentum. If you either increase the rotational inertia, increase the rotational velocity, or increase all of the above, the angular momentum will increase. We also have to consider the conservation of angular momentum; the equation is the rotational inertia multiplied by the rotational velocity before is equal to the rotational inertia multiplied by the rotational velocity after. Based on this equation, we know that if we increase the rotational velocity, we will decrease the rotational inertia which was the best option in this scenario. However, the opposite can happen; the rotational inertia can increase causing the rotational velocity to increase. Moving on, we also have to consider tangential velocity. This is the distance something covers over a certain amount of time. We would like our tangential velocity to be hight, because this means that the wheels will have to move a greater distance over a shorter period of time.
       The last physics concepts we need to take into account are the presence of work and calculating the force, the potential energy, and the kinetic energy. We are incapable of calculating the work the spring does on the car because this force and the distance the car is moving are not parallel; both the distance and force must be parallel for work to be done. We also cannot calculate the amount of kinetic energy because the velocity will not be uniform throughout the experiment. And since we are unable to calculate the kinetic energy, we are therefore unable to calculate the potential energy stored in the spring. Finally, we are unable to calculate the force the spring exerted on the car to accelerate it because the car did not have the same acceleration for every single test trial. Therefore, the spring exerted a different force on the car every time it was released.
       While this project was one of the most stressful projects I have ever worked on, it was also the most beneficial. I learned that sometimes you have to fail many, many times to actually succeed. I wish I could show you the video of our mousetrap car finally moving, but unfortunately the file will not successfully email to me. However, I will tell you this: there was screaming, there was happiness, and there were two girls collapsed on the floor crying tears of joy.

Second Semester Unit 2 Blog Reflection

It's hard to believe that another unit has gone by this semester and it is only February. Our units have been so short that they just fly by. This unit has seemed particularly easy, but I guess we will see how easy it was tomorrow during the test. Not only did we learn about work and power but also their relationship together. We also learned about kinetic energy, potential energy,the change in kinetic energy, the law of the conservation of energy, and machines. To start things off, lets talk about work. Work means that you are exerting a force on an object over some distance. It is equal to force multiplied by distance. Work is measured in joules which is one Newton-meter. We learned that there is a specific relationship between the force and the distance; these items need to be parallel to one another for work to be done. For example, when a waiter is carrying a tray and walking, he is not doing work because his force and distance are not parallel to one another. Also, you have to be moving some distance to be doing work. When you push against a wall, you are not doing work on a wall. However, your muscles are doing work because they are stretching and moving over a distance. You are still exerting a force on the wall, but since the wall doesn't move (or shouldn't move because maybe sometimes it does move) you are not doing work on that wall. Moving on, the next thing we talked about was power. Power is how quickly work is done. It is equal to work divided by time. We measure power in watts which is one joule/second. Here, we also talked about horsepower, which is how much work something does. One horsepower is equivalent to 746 watts. That's impressive! Work and power have a special relationship with each other. Think back to when we did the experiment running and walking up the steps. When we calculated the work for both running up the stairs and walking up the stairs, they stayed exactly the same. This is because neither the force or distance were changed. Work does not depend on time. However, power does. The answers for the power when running and walking up the stairs were very different to each other. Because it took a longer amount of time to walk up the stairs, there was less power done. Accordingly, running up the steps took a lot less time which meant there would be more power. This concept can be complicated to grasp at first, but once you think about it a few times it starts to sink in. Next, we talked about kinetic energy, potential energy, and the change in kinetic energy. We know that kinetic energy is the energy of motion. The equation for this is one half of the mass multiplied by the velocity squared. To calculate the change in kinetic energy you calculate the initial kinetic energy and subtract that from the final kinetic energy. The change in kinetic energy is equal to work. Potential energy is stored energy. To calculate the potential energy, you multiply the mass, the gravity, and the height together. Then, we learned about the law of the conservation of energy. This law states that energy cannot be created or destroyed. It may however be transformed from one form into another, but the total amount of energy never changes. We talked about how in cars, energy is transformed into heat, and that is why an engine heats up. We also talked about this in terms of a ball falling to the ground. Before the ball has started movement, it might have 1000 Newtons of potential energy and zero Newtons of kinetic energy. Then, as the ball reaches the halfway mark, it will have 500 Newtons of potential energy and 500 Newtons of kinetic energy. Then, right before the ball reaches the ground, it will have zero Newtons of potential energy and 1000 Newtons of kinetic energy. The amount of energy will be constant throughout the fall. Finally, we learned about machines. A machine helps decrease the force needed to exert on an object and still keeps the work the same amount. There are two different kinds of work here, the work in and the work out. While both of these final values will be the same, there is still a difference between the two. The work in has a larger distance which results in a smaller force whereas the work out has a smaller distance resulting in a larger force. One machine is an inclined plane or ramps. These ramps help use energy more effectively. There are many other kinds of machines that we use in our every day lives and just might not know it. I feel that unit has gone particularly well. I still think that my confidence in solving physics problems is increasing. One thing I have not done that much in this unit is talk in class. I think that I could benefit from doing this more. Similarly, I have also been thinking of different methods of studying for tests to improve my grades each time. I have been working on a study guide that has all the concepts we studies this unit. It seems to be working well since I feel confident about this material but we will see tomorrow come test time.

Inner Tubing Photo

        This summer, my friend Rachel and I went on a weekend trip to a mountain house with my parents. While there, we went inner-tubing. The course we went down had a similar set up to that of a roller coaster where there are steeper parts and flatter parts. When Rachel and I were about to go down a steep part, we had a large potential energy. However, as we were released down the course, our potential energy decreased and our kinetic energy decreased. This process occurred at every slope. We always had the greatest potential energy right before reaching an incline, and always had the most kinetic energy towards the end of the incline. It was a lot of fun, but the down side was we had to climb up a steep hill every time we finished the course.