Mouse trap car post

Mouse trap car Blog post
Video of our car in action

Sydney and me with Clarence (car) after our timed run.

Clarence the three wheeled monster clocked in a t covering five meters in 4.23seconds taking 4^th place

How did Newton’s Laws apply to the performance of the car?               

·         The first law states that objects at rest will say at rest, and objects in motion will stay in motion unless acted on by an outside force. This law is used in the car as the spring acts as the outside force to start the car, and then by utilizing the smallest amount of friction an outside force the car will continue to roll forward.

·         The second Law states that acceleration equals force over mass. This is seen in the car in the lever arm of the spring, as well as the accounting for mass. Since the spring creates a set amount of torque creating a longer lever arm decreases force, but as this happen the longer lever arm moves farther distance.  A shorter lever arm uses more force to produce the same torque, and is therefore faster. Weight and mass on the care is a thin line, on one side it is not heavy enough, and on the other it is creating too much friction with the ground and will not work.

·         The third law states that every action has an equal and opposite force. This is seen in the car with the wheels, as wheels push car back ground pushes car forward. The car creates more friction forward then backward and therefore accelerates on to the track.

Which Part of your car relied on friction? How did you utilize it?

            Our car relied on friction in the wheels, so that they would hold traction and be able to move on the ground. We accomplished this by using balloons and stretching them around so that they would be covered in rubber, and therefore very sticky. There are two ways to change friction one by adding weight so that the surfaces are pushed harder together, or changing the nature of the surface, which is what we chose.

How did the size of the wheels affect the cars performance?

            I think we chose wisely in choosing a wheel which was not to large or small. We used CD’s, and their large diameter was very helpful because each rotation covered much more ground than a smaller wheel such as bottle cap. This is seen in the real world with fly reels, as larger reels are made in a large arbor which has a much greater diameter than mid arbors which only pick up a fraction of the line in each rotation. I think our choice of using a wheel which was not very thick was very beneficial, as it is comparable to a road bike tire and that of a mountain bike.

What did the size of the wheels mean for torque, and rotational inertia?

Larger diameter wheels mean larger torque, since the wheel radius acts as a lever arm. A larger radius means that the weight is going to be spread farther away from the axis of rotation, and therefore have a larger rotational inertia. Though a larger diameter wheel allows you to cover more distance in a single rotation it is also much harder to get going due to its larger rotational inertia.

Why can’t we calculate the amount of work the spring does on the car? Why can’t we calculate the amount of potential energy stored in the spring, and the amount of kinetic energy used?  Why can’t we calculate the force of the spring on the car?

            We cannot calculate the amount of work the spring does on the car since the spring is not parallel with the ground, and therefore no work is done. We cannot determine potential energy since work = change in kinetic energy, and kinetic energy = potential energy, and since work cannot be determined nor velocity since it is constantly changing finding the energy is impossible. We cannot find the force because we cannot calculate work, which would allow us to solve for force since work = Force (Distance).

Reflection

            Our design did not change at all between drafting and finished product. The only major change was the difference in use of robotics fasteners to on the forward wheel The change was prompted by the hot glue on the forward axle from becoming dislodged causing us to lose our front wheel.

The only major setback we experienced with performance was the tendency of the car to get stuck in the rut of the floor boards, and to eventually stop over a foot short. To address this we put masking tape on our front wheel so that the surface would be wider eliminating the ability of it to sink into a rut.

. To make my car go faster in the future I would use mono filament instead of a braided yarn as it would stack better on the axle allowing for more line under tension so that you will get more rotations on the axle allowing for a farther distance to be reached.

Next time I do a building project I want to spend more time tinkering with a working project so that I can tweak it to be better. In both robotics and this project I felt that we built a decent product but did not meet its full potential due to lack of time experimenting with it.