Partner: Kim Low
Mouse Trap Car Lab
Teamwork:
Kim did an amazing job with this mouse trap car. We worked on it at her house on Sunday October 23rd for nearly 5 hours. We were not able to get our many cars to move however, they looked very fancy. We came into class the next day and asked Mr. Elwer for some tips. Then Kim went home and we discussed how we could build the winning car! I unfortunately had a Cross Country meet so I was not there to construct our final car but, I did add the style and beautification of the car. She remained positive the whole time and I definitely could not have done the project without her. We were able to form a friendship and partnership that we would like to continue the rest of the year for our projects.
Intro:
The purpose of this lab was to design a car that is able to move, powered by a single mouse trap. We will use what have learned about forces and vectors to "power" our car by using the "snapping part" of the mouse trap as the "arm” and attach it to the axle of our car, which will cause the axle to spin resulting in a change in the car's motion. The rules were as follows: no outside help, no looking up the best design on the internet, and no modifications to the spring on the mouse trap. The minimum displacement for the car to travel and receive full credit was 5 meters.
Hypothesis:
Our first hypothesis was "a long, light-weight body for the car, large wheels in the back, and one small front wheel that had little friction would be the most successful." We figured the larger the wheels were the more distance we could cover for every axle turn. We hoped that the small front wheel would help the car's motion due to its low friction after the axle's began to spin. After three different designs failed we went "back to the drawing board." We came up with the idea of a "hanging mouse trap" on the car. Which means the mouse trap hung from the axle between the two records. This caused the car to experience little to no friction due to less weight and less friction. However, the key to this design was the wheel alignment as well as, the weight and force the mouse trap will give off.
Materials:
* Two LP records (Alan Freeman’s History of Pop)
· 2 squares of cardboard ( approx.. 4inx6in) with a 1in square cut out of the middle of one end
· 1 square of sturdy light weight foam presentation board (approx. 4inx4in)
· A length of threaded 3/16in metal rod
· A metal saw
· An X-ACTO knife
· 6 10ml nuts
· 4 10 ml washers
· 4 small bolts and nuts
· 8 small washers
· Pliers
· Assorted wrenches
· Duct Tape (preferably purple)
· Wax coated (physics) string
Experimental Design:
All variables that we manipulated were for the car's design. We had control of the following: wheel size, axle size, and components of the car's body. In our first design we used a long, metal body with three wheels, one in the small wheel in the front and two large records in the back. Our front wheel was a wall paper roller which was attached by the handle to the bottom of the car. Our back wheels were LP Records and were attached to the axle by way of a threaded 3/16 axle. They were held in place by various nuts and washers, and there were two sets of nuts on either side of the body of the car to ensure that it did not slide back and forth on the axle too much. Our arm was a stick of bamboo tied to the mouse trap by a wax covered string. However, this design was way too heavy and the mouse trap was not able to move the car. Our next design, we shortened the car's body a lot hoping to make it lighter and get some motion. However, this design also failed. We were frsutrated by then and destroyed our car and took all of the components of it and attached it to a long body made of sturdy light-weight foam. Our car still would not move, so we deicded that it had to be our front wheel. Also that our mouse trap may have been to weak to pull the "arm" attached to our axle at all and we might need to add a “transmission”, or a small section of the axle that is enlarged so as to make it easier for the mouse trap to begin pulling it. Instead, we talked about it and decided to approach the car a whole new way with a "floating mouse trap". We drew up a plan in which the mousetrap hung freely from the axle in between the two records. We literally prayed to God that the small focused weight in the middle of the car would help it to maintain its momentum after it began to “free-roll” with no more power from the mousetrap.
All variables that we manipulated were for the car's design. We had control of the following: wheel size, axle size, and components of the car's body. In our first design we used a long, metal body with three wheels, one in the small wheel in the front and two large records in the back. Our front wheel was a wall paper roller which was attached by the handle to the bottom of the car. Our back wheels were LP Records and were attached to the axle by way of a threaded 3/16 axle. They were held in place by various nuts and washers, and there were two sets of nuts on either side of the body of the car to ensure that it did not slide back and forth on the axle too much. Our arm was a stick of bamboo tied to the mouse trap by a wax covered string. However, this design was way too heavy and the mouse trap was not able to move the car. Our next design, we shortened the car's body a lot hoping to make it lighter and get some motion. However, this design also failed. We were frsutrated by then and destroyed our car and took all of the components of it and attached it to a long body made of sturdy light-weight foam. Our car still would not move, so we deicded that it had to be our front wheel. Also that our mouse trap may have been to weak to pull the "arm" attached to our axle at all and we might need to add a “transmission”, or a small section of the axle that is enlarged so as to make it easier for the mouse trap to begin pulling it. Instead, we talked about it and decided to approach the car a whole new way with a "floating mouse trap". We drew up a plan in which the mousetrap hung freely from the axle in between the two records. We literally prayed to God that the small focused weight in the middle of the car would help it to maintain its momentum after it began to “free-roll” with no more power from the mousetrap.
Data:
| | Run 1 | Run 2 |
| Displacement (exhausted) | 4.1 m | 4.8 m |
| Time (exhausted) | 5.4 s | 4.8 s |
| Displacement (Total) | 19.25 m | 17 m |
| Time (Total) | 37.2 s | 21.97 s |
| Mass in kg | 0.39 kg | 0.39 kg |
| Max Velocity | 0.76 m/s | 1 m/s |
| Average Acceleration | 0.14 m/s^2 | 0.21 m/s^2 |
| Average Deceleration | -0.02 m/s^2 | -0.04 m/s^2 |
| Force / Coefficient of Friction | F= .055 N / coeff.= .21 | F= .082 N / coeff.= .31 |
| Spring’s Applied Force | .055 N | .082 N |
| Work (Joules) | 1.06 J | 1.39 J |
| Power (watts) | .028 watts | .063 watts |
Conclusion:
All in all, Kim and I figured out that a long arm was not necessary for maximum displacement and that friction is key in this project. We also discovered that a key to getting the most force and movement for the car is in the type of string used. Our hypothesis was correct, with our projection that wheel to axle ratio would be a determining factor in overall displacement. However, an interesting fact was that a light car with centralized weight used correctly could increase the momentum of the car after the mouse trap completed its snap. In the end, our car was the best and had the most displacement out of the entire class mainly because of the wheel turn-over rate and because it rolled in the straightest line. This was due to our precision in assembling the body of our car and placing it on the axle, as well as our extensive planning and testing of many many MANY different car designs.
