Voltage Resource

This video offers a great explanation of what Voltage is and how it relates to both Charge and DIFFERENCE in potential energy. It provides the equation for Voltage as well as providing a few examples to make sure viewers understand the subject well. I would recommend this video for anyone who is looking to learn about voltage or anyone who is reviewing voltage. The only problem that I see with it is that the video is a little long, longer than 9 minutes.

Mousetrap Car Reflection

1. 2.91 seconds. 2nd in the class, _____ in the grade.
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a. Newton's first law (an object in motion will stay in motion, an object at rest will stay at rest, unless acted upon by an outside force) applied to the moustrap cars because we had to figure out the right car design to allow the cars to continue in motion as per their tendencies. This means finding ways to have as little friction as possible in the design of the Car.

Newton's 2nd law (Acceleration is proportional to the net force over the mass of an object) was key in designing our cars as we had to find the best design to allow for a larger force and therefore a larger acceleration of the car. This meant having as little excess mass as possible and maximizing the force that was available from the mousetrap.

Newton's 3rd law (every action has an equal and opposite reaction) was key in the design of the wheels of the car. Without this law, the car would not go. The action/reaction pair in this circumstance is that the wheels push the ground back, ground pushes wheels forward.

b. The two types of friction present in the car were Rolling friction and Sliding friction. The rolling friction was present in the wheels rolling across the ground while the sliding friction was present whenever a moving piece of the car was rubbing against the static parts of the car. Friction in the moustrap cars was not good for the goals that we were presented with. We had to have as little friction as possible in order to have our car maintain a higher speed for a long amount of time and to allow the car to go the 5 meters. Our car's front wheels would slide against the eye hooks holding them in place, to fix this we replaced the front wheel with a 2 wheel design where the 2 wheels weren't near any other part of the car. We used friction to our advantage with the back wheels by wrapping balloons around them. This allowed for the car to get more grip on the ground via friction and therefore had an easier time accelerating.

c. To decide the number of wheels we had to take into account how the car's turning would be affected by the number of wheels present. We found that our 1 wheel design that we originally had would often turn towards a wall. This was when we replaced the 1 wheel with 2 wheels that offered more stability. We used smaller wheels in the front of the car and bigger wheels in the back axle. Having larger back wheels allowed for more tangential velocity while having the same rotational velocity, this means that more distance will be covered with each rotation of the axle. Having smaller front wheels allowed for both the stabilization of the car and also allowed for as little friction possible to be present.

d. The conservation of energy related to the car as to have the car go the requested 5 meters, the car's design had to conserve energy as it went, meaning that we had to have as little friction present as possible. The car also had a set amount of spring-potential energy stored in the spring of the mousetrap. This energy was transferred to kinetic energy when the mousetrap pulled on the string connected to the wheels of the car, therefore making the car move forward. 

e. Originally we had a large lever arm to try and disperse the force over a long distance, but after that design failed we removed the elongated lever arm and used only the distance of the mousetrap. This allowed for more pulling force as Torque= Force x Lever arm. With the same amount of torque and a shorter lever arm, there must be a bigger pulling force to compensate. The power output of the car was increased when the lever arm was shortened for our car as the time to cross the line was decreased, and since power= work/ time and the work was the same, a shorter time meant more power. 

f. Rotational inertia determined how hard it would be to start and stop moving the axles which were attached to the wheels of the car. Rotational velocity determined how fast the axles were rotating, this determined how fast the wheels would rotate. Tangential velocity was determined both by the size of the wheels and by the rotational velocity of the axles. Bigger wheels and high rotational velocity meant that the tangential velocity would be high. 

g. We cannot calculate the work that the spring did on the car because the spring pushed in a direction that wasn't parallel to the distance covered by the car all the way through the path of the spring. We cannot calculate the potential energy stored in the spring because each spring was different and we do not know the distance it was pulled back, we did not know its weight either. We do not know the velocity of the cars and we do not know mass of the cars. We cannot calculate the force the spring exerted on the car to accelerate it because this is the real world and some of that force and energy will be lost due to friction and noise and other variables. 

A. Our final design used a different, 2 wheel front wheel design, and a different, shorter, lever arm design. These changes were prompted by the fact that our car did not go the 5 meters and that it did not go very fast. 

B. The major problems encountered with our car included the friction caused by the front wheels rubbing against the eye hooks that held them in place, and the lever arm's length which changed the force output of the mousetrap. We solved the wheel problem by using 2 wheels that were spread out in the front of the car, away from the car as a whole. The lever arm problem was solved by removing the elongated lever arm that we had previously added. This taught me that even the smallest changes can make a huge difference as each part of the car built on the parts previous to it. 

C. If I were to do this project again, I would have started without the use of an elongated lever arm, and I would have built wheel designs that would minimize friction. I would also use a chassis that had a lot less mass and would therefore be moved more easily with the same force.