Mousetrap car blog post

A. Explain how Newton’s first, second laws, and Third Laws apply to the performance of a car.

            Newton’s first law states that that every object continues in a state of rest or of uniform speed on a straight line until acted on by a non-zero force. This connects to the performance of a mousetrap car because while the car was placed at the line, with the mousetrap set, it was at rest. It did not move until acted on by a non-zero force. This force was the mousetrap when it was set off. This non-zero forced caused the car to be set in motion. Newton’s second law states that the acceleration produced by a net force on an object is directly proportional to the magnitude of the net force, is in the same direction as the new force, and is inversely proportional to the mass of the object. This has something to do with the mousetrap cars because if the net force, strength of the pull of the trap, was weak then the acceleration of the car was weak. If the pull was very strong, like the one in Meredith and Isabelle’s car, then the result will be a super fast acceleration like theirs was. Newton’s third law states that whenever one object exerts a force on a second object, the second object exerts and equal and opposite force on the first. This connects to the performance of a mousetrap car because when the CD wheels are pushing off of the ground, the ground is also pushing off of the CDs. Likewise, when the trap pulls the string, the string pulls the trap.

B. What are the two types of friction present? What problems related to friction did you encounter and how did you solve them? How did you use friction to your advantage?

            The two types of friction present in this experiment were: The friction between the string and the axis, and the friction between the CDs and the ground.  Friction was a bigger problem then anyone thought. In our first car, the string did not have great friction with the axis. It would slip and slide on the axis and barely pull it with the amount of force expected. There was not enough friction in that instance. In our second car, friction was great. The string had great friction against our metal axis. It pulled the axis with the expected force and allowed our car to go five meters. We basically solved the friction problem by luck. Spontaneously building a new car with a different axis helped conquer our friction problem. The friction between the CDs was not as difficult as a problem to overcome. We simply just put cut up balloons around the edges of the CDs so that they wouldn’t slide on the tile floor.  One way that we used friction to our advantage was by adding more to the back wheels and giving the front wheels as little as possible. This helped because with the added friction on the back wheels, it made the car more capable of receiving the greatest push possible. By leaving the front wheels naked, we allowed the to just roll as fast as they could. If there were balloons around the front wheels it would also just slow our car down.

C. What factors did you take into account to decide the number of wheels? What kind of wheels did you use in each axle? What is the effect of using large or small wheels?

            When choosing the number of wheels we really didn’t take much into account. We honestly just thought about how most car wheels systems operate and worked off that. That took us to our decision of four wheels. Stability though, is a huge factor when choosing the number of wheels. We used CDs and DVDs. They are both very slick circles with a hole great for the placement of an axel. We found out that DVDs weigh more than CDs so we placed those in the back and put the CDs in the front. This was helpful because you want more weight in the back where the speed is delivered from, while you want the lighter wheels in the front so that they don’t slow down the car.  All of our wheels were the same size. The benefit of using large wheels was that they were better if you wanted to go long distances, while small wheels were better for faster rotations and smaller distances.

D. Discuss the conservation of energy in how it relates to your car? Be sure to include information about how your car’s use of potential and kinetic energy.

            The conservation of energy states that energy cannot be created nor destroyed. This means that all of the energy our car had was used in some way. When the car is at rest with the trap not set it has no potential energy. When the trap is set and the car is at rest it, then does have potential energy. This is because now that the trap is set, energy is in a stored state.  When released the car will now have kinetic energy. Kinetic energy= ½ mass x speed. When the car gains speed it then gains kinetic energy. Due to the conservation of energy all of the potential energy will eventually be transferred to another form of energy. In our experiment, that transfer was to kinetic energy and thermal energy.

E. What was the length of your lever arm? Discuss the effect of the length  of the lever arm in the a. the pulling of the force and b. the power output of your car.

            We added no lever arm to our working car. We realized by trail and error and help from the UNCA student. He said, “the longer the lever arm, the longer the distance.” That might have been true, but it did not work for us. Also a longer lever arm increases the torque of the car. So in our second attempt at a car we did not add a lever arm. The lack of an extended lever arm allowed the force from the trap to be delivered to the car faster. I honestly have no clue how a shorter lever arm worked over the longer one. One problem we came across with the longer lever arm was that is made our car unbalanced, which led to the change in direction of our first car.

F. What role did rotational inertia, rotational velocity, and tangential velocity play in your functioning car?

            All three of these factors played a huge role in our functioning car. Rotational inertia is the property of an object to resist changes in its rotational state of motion. If there had been no friction, no matter how slow our car would have been, it still would have gone the required distance because there was no outside force stopping it. Rotational speed and Tangential speed were the same for both sets of wheels. They wheels we  used were the same size, therefore their rotational speed would result in the same number of rotations in any certain unit of time. The tangential speed is directly proportional to rotational speed. If our wheels had the same rotational speed, they would also have the same tangential speed, which is the direction of motion that is tangent to the circumference of a circle.

G. Why can’t we calculate the amount of work the spring does on the car? Why can’t? t we calculate the amount of potential every that was stored in the spring and the amount of Kinetic energy the car used? Why can’t we calculate the force the spring exerted on the car to accelerate it?

            We can’t calculate the amount of work the spring does on the car because we don’t know the amount of force that the spring acts on the car with. Also we can’t find the change in Kinetic Energy either. We can’t calculate how much potential energy was stored in the string because 1. We just don’t know how much force the string is holding, 2. The car is not elevated, therefore we cannot figure out the potential energy it holds. We can’t tell the Kinetic energy the car used because we didn’t even know the potential energy. According to the conservation of energy, no energy is destroyed or created. Therefore all that potential energy would come out as Kinetic energy and heat. We can find the kinetic energy at one point, but it would be irrelevant because we don’t know the potential energy.

REFLECTION

A. How did your final design compare to your original design? What prompted the changes?

Well our first design was stellar. It worked the first time we tried it and so we left it alone for the weekend, came back, and it wasn’t working. We tried so many things like adding a lever arm, straightening the wheels, adding more and less rope but nothing worked. For some crazy reason, I spontaneously just built a new car. Our old one was frustrating so  i made a new one not to beat the old one but just to relieve stress. I like to build. Turns out that that car was the one that work and went five meters the first time I tried it. We made a few adjustments to keep the front wheels straight. Also we taped the string to the back axis just so that coiling it would be easier.

B.  Discuss major problems encountered in the performance of your car and what did you do to solve them?

            I simply built a new car that worked. When I say we tried everything on our first car and nothing worked that I exactly what happened. We did everything and changed everything possible. Building a new car was our last resort and sort of our only option. The biggest problem was the fact that we started early and finished our project. We were so content that we had completed it way before everyone. We enjoyed our weekend and then came back to a nonfunctioning car. To solve this we spent countless hours working in the lab to fix it. Nothing worked and that lead us to the construction of a new car.

C. If you were to do this project again, what would you do differently in the future that could make you car fast?

            I would make everything as small as possible. Is seemed the faster cars were the ones with the least amount of added items. Isabelle and Meredith used the trap as their chassis and that is why they were the fastest. Everything must be small, I would even make smaller CDs. I am actually going to build another mouse car just because I know I have the potential to make a car as fast as theirs.