Mouse Trap Car

Mouse Trap car? What could this be? A Moving mouse trap? Yes!
Our assignment was to create a car out of anything we wanted or gathered and make it powered by the force of the mouse trap and it had to go 5 meters.

How we constructed it

For this project, Winston was my partner. What we did was construct a 4 wheel car, using metallic disks for wheels. The main body of the car was made out of wood we got from our local Lowes store, and so were the axils. For the axils to spin in, we stuck them through some pvc pipe and fastened it to the car's body. Then, we hot glued the mouse trap to the car and attached a lever arm with a string, which we later changed to rubber band. This rubber band was to wind up on the back axil, pulling the lever arm of the mouse trap, so it could, when let go, run by being pulled by the elastic and mouse trap combined. We made sure to not tie it onto the axil because if we did, once done unwinding, it would cause the wheels to stop.

Video of our car

In this video, are car just made it to the 5 meters mark, but then rolled back an inch.
We did more test after this video, but with this video our time was about 10.03 seconds. We calculated the velocity of the car to be, using v=distance/time, 0.49 meters per second.

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So what does this have to do with physics?

This mousetrap car brought all of the 3 of Newton's laws together in one project. How? Well, Newton's first law states that an object in motion tends to stay in motion unless acted upon another force, once we got that axil in motion from the mouse trap, it will want to continue to stay in motion, or rotate. The car also was affected by this, once moving it was moving, but the friction from the pipes and the ground made the car slowly slow down which was the "acted upon another force". The only thing that could prevent that is friction with the ground. Adding the free rolling wheels reduces this, but frictional forces on the axil must be reduced to maximize free rolling.

The wheels pushing the ground back, the ground pushing the wheels/car forward, and the rubber band pulling the axil, the axil pulling the rubber band, were both examples of Newton's third law. This law states that every object has an action and reaction force. This pushing car also explains the acceleration=Force/mass. This was Newton's second law. The bigger the mass, the less acceleration, but the bigger the force, which we did with a rubber band increased our acceleration, but since we had a big mass, it didn't cause that much of an increase.

More about the wheels, in the latest units we learned about rotational inertia. Our wheels for our car were somewhat bigger than others, why did we choose them big? Doesn't more mass cause less acceleration? Yes, more mass does cause less acceleration, but our wheels were very thin. The more mass not he outside of the axil would cause more rotational inertia, which is bad, meaning it wouldn't rotate easily. The reason we chose them having a bigger diameter was because this increased the tangential velocity, which is the time/speed it takes to do one rotation on the outside. Since we had the force in the axil of the wheel, the outside had to spin faster to do what one slower rotate in the middle did, so our car went, or was supposed to go faster, this is explained more later in this blog. Also, why our axil rotated was because when the mouse trap set off, it caused torque which was rotation. We added a longer lever arm to increase how much of the axil was going to spin more, not to increase the force, because when lever arm increases F decreases. the lever arm was to increase the rotational velocity of the axil.

The mouse trap stored elastic potential energy when it was set, this energy was conserved. It was conserved because once it was released it was transferred into kinetic energy, which the ability/wanting to move, which the car did with this forced spinning axil. This spring on the mousetrap was setting off force in an upward then downward way while the distance of the car was going forward. We know work=force times distance, but the force and distance aren't parallel. Potential and kinetic energy are equaled to the change in work, and since there is no work, we couldn't find how much of these energy there was in this car. We can't calculate the force because it's in different ways/areas.

Reflection

Our final car changed from what we planned. What we planned was a small car, but powered the same way. We ended up with a big piece of wood as the base. What caused this big car to be big was we needed materials so we rushed to get them not thinking of the physics behind this project at the time, once we started, then is when we knew we should've went smaller. The major problems was that our axils for our wheels didn't have anything to rotate in, except some hoop we made from sticking tape together. We resolved this problem by using pvc pipe so the axil ran smoothly through it. If we did this project again or any building project, we would probably go smaller, depending on the project, think of all the physics concepts before the materials, and make sure everything fits perfectly once we get the materials, because if you have a smaller axil than its hole to rotate in, then it's going to start turning a lot, which wastes energy.