Physics Analysis

After doing calculations, we were able to find our mousetrap car's potential and kinetic energy.

Kinetic Energy: 1/2(mass)(velocity)^2
                            1/2(.192)(1.49)^2
                            =.2131 J
Potential Energy: (avg. force)(distance of string)
                          (2) (.055 * 3.14)
                          =.3454 J

These calculations make sense because while the kinetic energy is less than the potential energy of the mousetrap spring, friction in the wheels and body of the car will cause the thermal energy to rise and the kinetic energy to decrease. The length of the lever arm was multiplied by the average force to find our potential energy which makes sense since it is half of the length of the mousetrap itself. The efficiency of our mousetrap car is 61.7%.

Because this mousetrap spring is not that strong, it makes sense that both the Kinetic and Potential Energy are low values. The Total Energy never changes, but instead converts between Kinetic, Potential, and Thermal Energy (created by friction).

Our greatest problem dealing with friction was between the axles and body of the mousetrap car. The axles turning would create friction against the cardboard body and convert some of the spring's Potential Energy into Thermal, instead of Kinetic Energy that would make the car accelerate.

Phase 4: The Final Trial

We performed three trials in class today, and discovered that our mousetrap car's maximum velocity was 2.545 m/s.

This is the video that captured our fastest trial, Trial #2.

After analyzing the footage in Logger Pro, we found the maximum velocity of 2.545 m/s.

Final Thoughts on our Final Trial

With our previous car we only reached about half of the velocity that we reached today with our new car and even when we remade our car, it didn't initially have the results that were received today. With tweaks to our car, we felt as if we found ways to maximize our kinetic energy. We tried new things such as a different way of setting up our project and that turned out to be very beneficial. Although we learned what to avoid with our old car we wish we had more time with the new car because we feel if we had worked on our second car with the complete duration of the time allotted to us, we could have even further maximized our kinetic energy, but we still are proud of the car we put together.

Starting From Scratch

After modifying our mousetrap car today in class, we found that the complications were the eye hooks, the string, and the cardboard body. The eye hooks were too loose around the axles, and were not strongly attached to the body, so when we tried to run a trial the eye hook turned and the weak body bent in such a way that the string could not unwind and the axle could not turn. The string became tangled around the axle and around the mousetrap itself, making it so that the potential energy of the mousetrap spring could not be transferred into making the car accelerate. The cardboard body wasn't sturdy enough to support the eye hooks and the mousetrap, and bent when the wheels and axles turned.

When our modifications failed, we decided to construct a whole new mousetrap car, because the body and its connection to the axles all had to be replaced.

Our new prototype looks like this:

The body is a tissue box, and the wooden dowels (the axles) are going through the body, which proved to be a sturdier connection than with the eye hooks. The CD wheels are attached by corks to the axels. We remade the wheels to be wrapped in duct tape to provide traction. The body is held in place by tape wrapped round the dowel on the outside of the body. The mousetrap "engine" is hot-glued to the base of the tissue box, and a shorter piece of string is tied to the snapper arm and the back axle.

We only had time to run one trial with our new prototype, and it managed to accelerate at a decent velocity. This is a good start, but we still need to keep improving this model!

Diary Entry #3: Successes and Failures

Dear Diary,

In class on Tuesday, we ran a few more trials with our car and made various modifications.

The most successful thing was that the car was able to accelerate at a decent velocity in the several trials that we ran. We kept it in mind that we had to wind the string around the back axle without getting it tangled making sure it unwinds smoothly and to pull the mousetrap's snapper arm all the way back making sure that the spring has the most potential energy so in turn the car has the greatest kinetic energy during the run. We were going to capture the trial in a video, and then analyze the data to find its velocity, but ran into some complications.

The least successful thing was these complications: the mousetrap breaking off of the body, the shifting movement of the body on the axles, and the tangling of the string on the back axle. To tackle these problems, we first decided we should unwind and shorten the length of the string to avoid the tangling of it when we set the car. To address the shifting of the body on the axles, we wrapped duct tape around the dowels on the outside of the eye hooks, so that the body can no longer slide from side to side on the axles. This was wasting some of the energy that could go into making the car accelerate. Next, we will reattach the mousetrap to the body with a stronger adhesive, or use stronger cardboard or other material for the body itself.

We have a few modifications to address, but we feel that we are off to a great start!

Phase 3: Prototype

We completed our first trial yesterday and it went pretty well. Below is the video of our car being launched.

Obviously there is a bunch of stuff we would like to improve with our car, mainly the efficiency of the string, but we believe this is a good start.

Diary Entry #2: One Victory and One Failure

Dear Diary, 

Today in class we began the process of constructing our mousetrap car. We had some successes and some failures. 

Our Victory: 

• Getting the majority of our car done was a big success for us. We didn't think that it would take us a short amount of time to put together most of it. We were really content with our progress at the end of the period.

Our Failure:

• Noticing that the front wheels couldn't be the same size as our back wheels was kind of annoying because that's how we had planned for it to happen and it was our fault for not catching that earlier. We struggled to find an object that could become our front wheels until we decided to use cardboard, which is probably the best decision for us at this point.

At this point, we have come to realize that having failures and successes is common when it comes to a project like this. As we progress, we will continue to overcome our obstacles.

Phase 2: Construction

 In class today, we began assembling our mousetrap. Below are pictures of different elements of our mousetrap car in progress.

A CD for a wheel (a rubber band is taped around the edge to increase traction).

The mousetrap "engine" hot-glued to the cardboard body.

We screwed four eye hooks into the cardboard to hold the axels/wheels and the body together.

The body with the back wheels and axel attached to the body

(This was the model we had at the end of class). 

This video is showing the two back wheels moving as Kalina pushes it. During class today, we did not get to the point where the wheels could move using the mousetrap's potential energy because we haven't attached string to the snapper arm and axel yet.

Going forward, we will cut the two front wheels out of cardboard, and then attach the dowels and the wheels to the body. We also will need to harness the potential energy of the mousetrap by tying string around the snapper arm and the back axel, leaving extra string so that the snapper arm can be bent back and the string could be wound around the dowel, as mentioned earlier.