Thomas the moursetrap car took a cool 4.39 seconds to make it to the 5 meter finish line.He came in 4th place but Thomas the mousetrap car will keep on pushing to get better and better everyday!
Here one can see the almighty mousetrap car, Thomas!
As you can see the wheels are made up of CDs and we have a lever arm attached to the mousetrap that is then attached to a string that wraps around the axel of the car. The wheels have electrical tape on them to create a larger friction between the floor and wheel. And finally the body of Thomas the car is a piece of rectangular wood with the mousetrap glued on top! He was quite the racer!
A.
All three of Newton's first were used in the performance of our mousetrap car.
Newton's First Law
Newton's first law is, an object in motion/rest will tend to stay in motion/rest unless an outside force acts upon it. With that being said our mousetrap car wanted to stay in motion, however during the trail runs, our mighty Thomas car encountered a lot of friction, whether it was with the wheels and axel, the friction between the wheels and floor, or the friction between the string and axel. Besides the friction between the string and axel, friction is what slows the car down and therefore is a bad thing!
Second Law
Newton's second law determines the acceleration of an object by using to variable to calculate the acceleration, the net force acting upon the object and the mass of the object. In this case, the more mass the car has the more force needed to accelerate the car, and the less mass of the car the less force needed to accelerate the car.
Third Law
Newton's third law is, for every action, there is an equal and opposite reaction. With this being said we know that the has many different reaction/action pairs that cause the car to accelerate and slow down. The car pushes the ground backwards with the same amount of force as the ground pushes the car forward. As well as the string pulling the axel up with the same amount of force as the axel pulls the string down. This same concept is seen in the horse and buggy problem, there are many variables in making something move!
B.
Friction was a huge variable in this project, in every part of the car there was some sort of friction, whether it be between the string and axel, the wheels and the floor, or the wheels and the axel, friction was everywhere! Friction is determined by two things, the surface between the two, (smooth vs rough) and the mass of the object. There was good and bad friction in this project, we wanted a good amount of friction between the axel and the string in order for there the highest possible potential energy converted to kinetic energy. However friction between the wheels and floor caused the car to slow down and eventually stop, in order to increase the friction between the wheels and the floor to insure that the wheel would not spin was to tape the wheels. By taping the wheels we made the smooth surface of the wheels and floor to a 'rougher' surface. This insured that we would not have to worry about the wheels spinning but we did have to take the friction between the wheels and the floor into consideration. I think if I were to build another car finding a way to use three wheels efficiently or having as little friction between the wheel and axel and the wheel and floor would be necessary in order to make a fast car.
C.
Katie and I used two CDs and two small disks as our wheels, later on we discovered that although the smaller wheels had a much higher rotational inertia, it did not have have the large enough torque for the car to travel 5 meters. In order to fix this problem we attached two more CDs (four total) in the front. This was much better because there was a much larger torque than the small disks because the wheels were larger. The CDs needed more rotational inertia due to the distance from the axis of rotation and the edge of the wheel, and if the wheels would've been any larger the lever arm would needed to be smaller in order to compensate for the size of the wheel to make it function and have enough force to go 5 meters.
D.
The idea of the conservation of energy is simply, energy cannot be created nor destroyed, rather it can be altered from one state to another. The car worked by doing work and energy is necessary in order to do work. When we set the mouse trap we were giving the car a certain amount of energy, that energy from the trap is then transferred to the car when the mousetrap is released and the string unravels the axel causing the wheels to turn. The energy would decrease faster due to heat, sound, and friction.
E.
Rotational inertia, rotational velocity, and tangentail velocity are play a part in how the car functions
Firstly, rotational inertia is the measure of an object's resistance to change in its rotation. So with that being said we can then apply that to the size of the wheels. The diameter of the wheel whether it being small or large determines the rotational inertia, the larger the wheels are the more rotational inertia required (or more force needed in order for the wheels to rotate) the smaller the wheels the less rotational inertia required, so there is less force needed for the wheels to rotate.
However you must take rotational velocity into account in picking out the size of wheel you want to use for your car. Rotational velocity is the amount of times the object in our case the wheel rotates in a given time. The smaller the wheel the larger the rotational velocity would be therefore giving you a faster car, or larger wheels that have a lower rotational velocity causing the car to move slower.
So you have to take into account if you want to have a high/low rotational inertia or a high/low rotational velocity. By having larger wheels you will have a higher rotational velocity causing the car travel a farther distance with a slower rotational velocity therefore causing the car to move slower than having smaller wheels. Having smaller wheels will cause you to have a lower rotational inertia but giving you a smaller distance due to the amount of force and how many times the wheels will be able to rotate with that given force, but will have a higher rotational velocity. So you must find a balance between having a high rotational inertia/rotational velocity or a low rotational inertia/rotational velocity. In our case we used CDs and they provided us with a high rotational inertia but a lower rotational velocity.
The tangental velocity was the same because we used the same size wheel but the tangental velocity was smaller in the center of the wheel because it had to travel a lot less than the area on the outside of the CD to be able to complete the same rotation.
F.
We cannot find the amount of work the spring did on the car because the two forces are not parallel, and therefore now work can be done with the spring and car.
In order to find the potential energy of something we must use the formula PE=mgh. We cannot calculate the potential energy of the spring because
To find kinetic energy we must use KE=1/2mv^2, and since the velocity is always changing the kinetic energy cannot be calculated unless we had a radar to measure the velocity of the car.
In order to measure force we must know the work done and the distance, and because we do not know the distance the spring traveled therefore we do not know the work done, so we cannot find the force the spring exerted on the car.
Reflection
A. The final design of our mousetrap car was very different from what we had in mind at the beginning of this project. The change occurred on only a few days after we began this assignment, we had done a few test runs and the car did not seem to be functioning at full potential and when we went back to tweak it, I dropped it and completely broke it. So Katie and I were going to face adversity and a lot of it these next two days in order to complete the project on time. Our end product yet slow was quite mighty, it was much more measured out and neatly crafted. Our originally design was made up of two long knitting needles with two small wheels in the front and two larger wheels (CDs) in the back, we discovered that having smaller wheels in the front was holding back on the distance the car could travel. Our end product had four CDs and was shorter and made up of a rectangle piece of wood.
B. The two biggest problems we encountered were having to figure out how to make the back wheel axel stop getting caught and stuck with the string and figuring out that the smaller wheels were actually decreasing the distance of the car although it caused it to have more rotational inertia. We just had to experiment with the string and figure out how long it needed to be, how to wrap it around the axel, and how to make sure it would not get stuck between the axel and the frame of the car. We also had to experiment with other wheel sizes and found out that CDs were our best bet of getting the car to go five meters.
C. If I were to do this project again I would first do more research, I would also do more test trails on different sizes of wheels and see which wheel was the fastest. Then I would also want to try adding weight to the back of the car and see what that did, overall I would just do more trails and more experimenting.
D. If I were to build another mousetrap car I would focus more time on making sure that the wheels were lined up correctly and not wobbly, as well as fiddling with different frames like length and width size. I think then our car would go faster and straighter.
Here is our little Thomas crossing the finish line!
