Mousetrap Blog

My mousetrap car traveled 5 meters at a time of 2.59 seconds. This puts my teammate and I in first place.

Here is a video that shows my mousetrap car run. 

a) Newton’s first law of motion states that an object in motion or an object at rest wants to stay that way until and outside force is exerted upon it. This law is applicable to the mousetrap race at the starting line and at the finish line. Our car begins at rest and would like to stay that way, but when we engage the mousetrap, the string that is connected and coiled around to the back axel forces that axel to turn along with the wheels propelling our car foreword. At the finish line, our car is in motion and wants to remain that way, however the friction between the wheels and the ground slows the car down and eventually stops it. Newton’s second law, a=f net/m (acceleration is directly proportional to force and inversely proportional to mass) proved helpful for my team. When building our car, Isabelle and I used very few materials and kept our car simple. Because of this our car had a smaller mass, which allowed it to have a greater acceleration. Newton’s third law, which states that every action has an equal and opposite reaction is applicable to our mousetrap car similar to the horse and buggy problem. When the axel is turned because of the force the mousetrap pops with, the wheels are going to push the ground backwards and the ground is going to push the wheels foreword.

b) The two types of friction present are with the wheels and the ground, and the axel and the wheels. Attaching the wheels to the axel without them moving was challenging at first. Originally Isabelle and I tried to wrap balloons around the axel and fasten the wheels (cds) over them that way. This proved to be unsuccessful so instead, we used tape and that worked out well. The second problem we encountered with the friction was with our wheels and the ground. Our wheels are CD’s so the friction between them and the ground is little. To fix this problem we took the centers of two balloons and stretched them around the CD. This created better friction and propelled our cars nicely and smoothly.

c) We had always planned on using four wheels. That seemed to assure the smoothest ride and best stability along with simple construction. On each axel we used a regular sized CD. Using larger wheels would have been helpful because they cover a larger distance per turn of the axel. However our wheels worked out just fine. Smaller wheels would have been detrimental to our mousetrap car because it would have required our axels to turn more times because they cover a smaller distance per rotation. 

d) Energy is essential to make our mousetrap car move. Energy is neither created nor destroyed with the motion of our car. Energy is transferred from setting off the trap and releasing the potential energy it is holding. When set, the mousetrap holds a large amount of potential energy. When the mousetrap is set off, that potential energy becomes kinetic energy and shoots the car into motion.

e) We did not extend the length of our lever arm. When we test ran our mousetrap car it went 5 meters fairly fast. Seeing this we decided it wasn’t necessary to extend ours. However, I noticed that a great deal of the other groups extended their lever arm. Doing this they were able to increase their torque and use the greater distance to uncoil their string from their axis more quickly.

e) Rotational inertia was important to our mousetrap cars because it determined how quickly the wheels began to turn. Having solid wheels is key because they have a lower rotational inertia and will begin to move more quickly. The lower rotational inertial a car had, the greater rotational velocity it would have because it would be easier for the wheels to rotate. Each wheel of our car needed to have the same tangential velocity in order for the car to travel in a straight line. The straighter the line your car travels in, the quicker it will obtain a traveling distance of 5 meters.

f) We cannot calculate the amount of work that the spring does on the car because the distance is not measureable by us. We cannot calculate the amount of potential energy because the potential energy is directly related to the amount of work that the spring can do. We cannot calculate the kinetic energy because we do not know that amount of potential energy. Similarly we cannot calculate the force because the mass and the acceleration of the spring.

Reflection:

a) Our final design was almost exact to our original design. The only difference was that instead of using balloons to fasten our wheels to the axel, we used tape.

B) We didn’t encounter too many major problems. The only problems that we faced were when the balloons failed to fasten our wheels, and to fix it we tried tape which work well. And when we engaged our mousetrap the string would get caught, so to fix that we held the trap down and released it manually rather then with the sensor.

c) In the future I would keep everything the same and maybe extend the lever arm a bit. Personally I am very satisfied with the outcome of my mousetrap car and I am content with everything that we have.