Mouse Trap Car Madness

Over the span of the last week, Kennedy and I built a mousetrap car to apply the concepts we have learned over the year to a project.

Our car received 1st place in our class with a time of 2.98 seconds to travel a distance of 5 meters.

Watch the following video to see our little cart in action:

While building the car we took many physics conceptions into though. We had to show that we could complete the task at hand while also showing that we understood the physics behind it. The physics concepts we thought about when it came to the car are described below.

1. A light frame- We made a light frame out of popsicle sticks because acceleration = force/ mass. this tells us that the lighter the cart is, the greater the acceleration would be.

2. Large wheels- We chose large wheels(made of CDs) knowing that they would have a greater rotational inertia. Even though this is true, we figured that their greater circumference means that they travel a greater distance per rotation. The distance was what we were aiming to achieve over the speed, so we went with bigger wheels.

3. Axels- We used parts of mechanical pencils that were perfectly round. We chose these to promote ease of rotation. If the axels weren't perfectly cylindrical that would create friction which would cause the car to lose speed.

4. Ballons- We put balloons around our wheels to increase friction with the ground, because there has to be friction between the wheels and the ground in order to get the cart to move forward. There is an action reaction pair between the wheels and the ground. So, it order to get the car to go forward, we had to give it a greater push on the ground to make the ground give a greater push back.

5. Lever arm- We used a mechanical pencil attached to the wire of the mouse trap in order to have a longer lever arm. We used a lever arm to increase the time that the mouse traps snapping ability acted on the back axel. This allowed the cart to be moved by the stored energy for longer before it had to keep rolling because of momentum.

6. Yarn and Hook- We used yarn to attach the axel to the actually trap. This string is what caused the back axel to rotate as the trap closed. We applied the hook to create friction between the axel and the string. Without the hook, there wouldn't have been enough friction to make the axel rotate.

7. Mouse trap- Last but definitely not least is the trap. The wires of the trap have a lot of potential energy when it is pulled back. When the wire was released, it closes with a lot of energy. We were able to use the energy of the trap to make our cart move.

Physics Behind the Construction:

1. Newton's First Law: An object in motion(or rest) will stay in motion(or rest) until acted upon by an outside force. This is important because in order to keep the car in motion, you must take into account the outside forces and try to eliminate as many of them as possible.

2. Newton's Second Law: Acceleration is directly proportional to force and inversely proportional to mass. This is important because you must have a light car if you want it to accelerate quickly. 

3. Newton's Third Law: For every action there is an equal and opposite reaction. When building a mouse trap car, you have to keep this in mind, because there must be an action reaction pair between the ground and the car's wheels in order for it to move forward. 

The way our car related back to these laws are explained above.

Reflection

There are some differences between what we originally sketched and our final cart. The sketch shows the back wheels as CDs and the front as bottle caps. We should have also made the front wheels CDs a lot sooner, because thats what got our car over the line. We originally planned for the frame to light weight, which translated well to the final design. Other than the front wheels, everything worked out really well. Im very happy with the way our cart turned out. Especially because we won(only slightly competitive). If we had to do this project again, I would make sure to have the wheels all the same size. Also, I would make sure that they were all secured to the axels well, because we almost lost them a couple of times. Another thing I would do would be to better secure our lever arm, it got a little lopsided at times. At the end of all of it, I think our cart properly shows my knowledge of physics at work.