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For this project, we were assigned to build a reusable trebuchet that launches a projectile. Our goal was to send the projectile as far as possible by setting and releasing it without us having to fire it ourselves. The trebuchet itself required a base that sits on the ground, an axle held up by two legs, and a lever arm with load and effort ends. The dimension had to be at most 1 meter.
Our Trebuchet
Our Trebuchet
My group for this project was Alisa Costello, Joey Cook, and Daniel Gorel. We designed and built our trebuchet in the maker's space. We started off by accumulating our materials that we know was necessary for our trebuchet: a strong base, two legs, an axle, and a lever arm. For our first draft of our trebuchet, we used a PVC pipe as the lever and a large metal pipe for the axle. After assembling and testing it a few times, we found that the metal and PVC pipe create a lot of friction, preventing the projectile to travel its maximum distance. We also realized that the ratio of the lever arm of load to effort affects the the arm's full range of motion, not allowing it to follow through with the release. We tested our trebuchet changing the ratio of load to effort multiple times and found that the ratio of 1 to 1 allowed the projectile to go further (test results found in proof of efficacy document). We went back to the maker's space to rearrange our trebuchet. We disassembled it to find ways to improve it and make the projectile travel its maximum distance. Instead of using a PVC pipe that produces friction, we used a metal pipe and made sure its ratio of load to effort was 1 to 1. We also used a small metal bolt for our axle instead of a pipe and placed it as high as possible to maximize the potential energy. We made several modifications to improve and make sure our trebuchet was the best of the best!
The Final Product
The Final Product
Modifications:
Modifications:
lever arm ratio (load:effort): If the ratio of load to effort is 1:1, there will be a better range of motion, which results in more mechanical advantage.
stopper vs. no stopper: If there is nothing preventing the lever arm from stopping, it will have a full range of motion.
lever arm material: A metal pipe creates less friction compared to a PVC pipe.
type of axle: The friction created by the legs and the axle was minimized when we replaced the PVC pipe with a thin bolt, which caused the speed of the projectile increased.
projectile mass: There was more acceleration present when we used a projectile with less mass, so we used a projectile with a mass of 10 grams.
cup size: When we used a larger cup, our projectile was going through a tunnel, which prevented it to go farther.
number of rubber bands: With 7 rubber bands, there was enough tension to reach its maximum horizontal distance.
axle height: The higher the axle is, the greater potential energy, or stretch, our trebuchet had.
Proof of Efficacy Document
Proof of Efficacy Document
My proof of efficacy document includes a detailed description of our final product of the trebuchet, the modifications made to improve it, a data table and chart of the trials (Claim, Evidence, and Reasoning Poster), the calculations of our trebuchet, our main selling points, and pictures of the final product.
Main Calculations
Main Calculations
Spring Constant (k) = force/distance
The spring constant of our trebuchet was 37.7 N/m
Horizontal Velocity (v) = horizontal distance/time
Our horizontal velocity came out to be 18.48 m/s
Vertical Velocity (v) = (a gravity)(time of fall)
The vertical velocity of the projectile was 4.51 m/s
Total Velocity (v total) = a^2 + b^2 = c^2 (Pythagorean Thereom)
Using the Pythagorean Thereom, the total velocity of the projectile came out to be 19.91 m/s
Average Acceleration (a) = velocity/time
The acceleration of the projectile was 20.1 m/s^2.
Potential Energy (PE) = 1/2(spring constant)(distance)^2
The spring PE was 10.72 J. The spring constant was 35 N/m.
Kinetic Energy (KE) = 1/2(mass of ball)(total velocity)^2
The velocity total, 19.01 m/s^2, multiplied by the mass of the projectile, 0.01 kg, multiplied by 1/2 will get the KE, which is 1.81 J.
Reflection:
Reflection:
Throughout the course of this project, my group and I worked very well together. We all worked efficiently and got everything done that needed to be. There was minimal disagreements among one another and we all pitched in our own ideas to benefit the process of building the trebuchet and the final product of the trebuchet.
I felt that some of our strongest areas that was displayed during this process was Collaboration and Critical thinking. Our group was determined to complete the assignment. When we felt like our projectile didn't go far enough, we didn't give up there. We figured out the problem, made a couple modifications to improve the vehicle, and tested it again until we succeeded. This was a practice of critical thinking. We all worked to the best of our abilities.
I feel that we all had an open mindset about our process of making the project and completing the assignment. Each member's level of contribution and determination was high.
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