Mousetrap Car Lab

This car made 2nd place in our class and 8th out of 18 cars with a time of 3.72 seconds.

Newton's 1st Law of Motion:

An object at rest, tends to stay at rest and an object in motion tends to stay in motion unless acted upon by an outside force.

Applied:

The mousetrap car will stay at rest unless triggered. The mousetrap in motion will continue to move unless affected by an outside force. The outside force of friction between the wheels and the floor caused the car to slow down and eventually stop. 

Newton's 2nd Law of Motion:

Force is directly proportional to acceleration, and indirectly proportional to the mass of an object.

Applied:

We purposefully made our car have less mass because the less mass, the force will cause a greater acceleration to occur. 

Newton's 3rd Law of Motion:

For every action, there is an equal and opposite reaction.

Applied:

Wheels push backward on ground, ground pushes forward the wheels. String pulls axle, axle pulls string. Axle spins wheels, wheels spin axle. 

Two types of friction present:

1. Static
2. Kinetic

Static friction is the type of friction that keeps and object from moving. This would occur when the mousetrap car would not move.

Kinetic Friction is the type of friction that occurs when an object is moving. This would occur when the mousetrap car was in motion.

In regards to friction, my partner and I encountered a problem where the car would not move very far, due to a lack of friction. We fixed this by adding balloons to the rear wheels which gave the wheels more friction, but also more traction so that they would be able to move the car. 

My partner and I found a model where the car had 4 wheels, and thought that that would be a good idea. Using 4 CD's, this made for an easy configuration. The smaller the wheel, the less tangential velocity it has, so using CD's we were able to get a lager tangential velocity than we would have if we used bottle caps (as some other people did). 

Energy can neither be created nor destroyed. This means that energy can never be lost, just transformed into something else. When our car slowed down, energy was transformed into either sound or heat (another form it could take when 'energy is lost' is light, but that did not apply to our car). The car's potential energy can never be greater than what it had in the beginning, which will be the same amount of kinetic energy for the car. 

At first, our lever arm was as long as the distance between the bar of the trap to the back axle. This was a problem because once it unwound from the axle, it would stop the car. By lengthening the lever arm, we found a solution for that problem, but by increasing the lever arm, we lessened the force which meant that our car would go slower. 

By using a CD, rather than a hoop, there was less rotational inertia for our wheels, because the mass was closer to the axis of rotation than the hoop's mass would have been. 

We can't calculate the potential energy that was stored in the spring or the kinetic energy, nor the amount of work the spring did not the car, nor the force the spring exerted on the car to accelerate the car.

REFLECTION:

Our final design was very similar to our original plan. One change we made was instead of using soda-can-taps to keep the front wheels in place, we used zip-ties. The zip-ties were better to use because they were more predictable, and were easier to adjust. Another change was that instead of using balloons to keep the front wheels attached to the axle, we used electrical tape. This was better because the electrical tape was a smoother surface which enabled us to put the wheels where we wanted to and kept them in that place (but also allowed for changes if we needed to). The electrical tape did not completely solve the problem of keeping the wheels centered, but it was much better than the balloons we were using. 

One major problem we encountered was our car stopping because the lever arm was too short. We solved this by increasing the length of the sting used for our lever arm. Another problem we had was keeping the wheels where we needed them. We originally used balloons to keep the front wheels attached to the front axle, but they would not keep the wheels where we needed them, causing the car to run into the wall a lot. By replacing the balloons with electrical tape, this enabled us to more predictably adjust the wheels and keep them where we needed them to be.

If I was to do this project again, I would spend more time on the length of the lever arm. I noticed that by the time the car slowed to a stop, there was still extra string. I would have shortened the lever arm, making the force exerted greater, as well as the acceleration.