5 Discussion and Conclusions
5.1 Key findings
1. We have found out that we must have a suitable amount of friction on the wheels of our car so that the car will not skid or stay at the exact location not moving friction is important for the car to move.
2. The mass of the car affects the performance of the car. Since inertia varies with mass, the greater the mass of the car, the greater the inertia. The car should not be too heavy or too light. It should be just sufficient for the inertia of the car so that the car would stay in its state of motion for a longer time after the spring is fully released, allowing the car to travel further.
3. The size of the wheels affects the distance the car travels. A bigger wheel (greater wheel diameter) will enable the car to travel further as each rotation of the wheel travels a greater distance due to the circumference. A smaller wheel (smaller wheel diameter) will enable the car to travel less as each rotation of the wheel travels a lesser distance due to the circumference of the wheel, however acceleration can be achieved easily for smaller wheels as it requires less force as compared to large wheels.
4. The length of lever extension affects the performance of the car. When the lever arm is long, it creates a greater circumference during the period it is released. This allows more string to be coiled and pulled, thus increasing the total distance travelled. However, all the resistive forces will be acting on the tip of the lever arm since it is where the energy transfer take place and the string is coiled. so if the lever is long, the perpendicular distance of resistive forces to the pivot of the lever is great. Hence, the moment exerted by the resistive forces are high. as a result, more of the force exerted by the spring will be used to overcome the resistive forces and thus, there is less power to drive the car.
5. The chassis affects the performance of the car. The chassis should be made of a strong and sturdy material to be able to withstand the compressional force.
5.2 Comparisons with other designs based on research
By comparing our design with other designs based on research, we found that our car is slightly more stable than a three wheeled car as the balance of the car will be better which will slightly affect the direction of which the car is moving. This will affect our displacement of the car from the starting line if the car moves out of the designated track and it will be a huge disadvantage to us.
The wheels used on the cars based on research and the wheels used on our car are of different sizes. Thus, the distance that the car travels will differ due to wheel to axle ratio.
5.3 Evaluation of engineering goals
Develop a MouseTrap Car with the following specifications:
- Uses only the MouseTrap provided as the only energy source
- Has a maximum length of 30 cm, width of 10 cm, and a height of 10 cm
- Can travel a minimum distance of 5 meters carrying an egg (the egg will be provided by the teacher)
- All time-lines have to be adhered
(a) We used the mousetrap as the only energy source. (Complied with the engineering goal)
(b) Our car’s overall length is 34 cm, overall width is 9.5 cm and overall height is 12 cm. (Did not comply with the engineering goal, however, negligible as we did not exceed the size limit by more than 5 cm)
(c) Our car can travel a distance of up to 10m. (Complied with the engineering goal)
(d) We adhered to all time-lines. (Complied with the engineering goal)
5.4 Areas for improvement
Lever can be longer so that we could increase the length of the string for the car which will lead to a greater distance that our car can travel.
The egg holder can also be made more stable so that when the egg is put in onto the car, the egg will be more stable and not move around which will allow the ergonomics to be better.
A slight increase of lubricant will allow the wheels of the car to move more smoothly without much friction as when the axle comes in contact with the pipe wall mount, it will have lesser contact which allows it to travel further.
The chassis can be made longer so that we could increase the length between the hind wheel and the mouse trap car. Thus this would lead to an increase in distance travelled as more string will be attached to the wheel.
5.5 Practical Applications
A powerful spring can be used to power a car for short distance.
A powerful spring can be used to start up a car for a short period of time before switching to the usage of engines, thus it can minimise the amount of energy (e.g. petrol, electricity, etc.) usage by the car.
5.6 Areas for further study
We should research on minimising the cost of materials that are more suitable for the design of our car. .
We can also research on the effective use of gears and other mechanical components to improve the performance of the car.
We can also research on minimising the amount of friction in our car such as the friction generated between the surface area of the axle in contact and the axle holder.
We can also research on improving the aesthetics and efficiency of our car design.
DiSpezio, M. (n.d.). Building a better mousetrap car.
Retrieved from http://www.pbs.org/saf/1208/teaching/teaching.htm
William James Mason Jr. (n.d.). How to adapt a mousetrap car for distance.
Retrieved from http://www.wikihow.com/Adapt-a-Mousetrap-Car-for-Distance