Proof of Efficacy of Trebuchet
Our assignment was to make a device that sends an object a distance. The device must stay in one place and be completely reusable. It also must have a base that sits on the ground. Keeping the device portable, it must have all dimensions less than one meter. Our team built a trebuchet that was easy to set, but fired a far distance. Our first model had two 35.5 cm legs, with a large base. Our projectile was a 12 gram clay ball with a 10cm string. We also started with a firing carpenters nail perpendicular to our arm. We made many changes to our device to make it more effective.
- Firing Nail- After testing six different angles for our trebuchet’s firing nail, we have concluded that the optimal angle is ten degrees backwards from 90 degrees. A firing nail is one of the most important parts of a trebuchet, it determines the height the projectile will be released, which determines the distance of the projectile. Since the furthest distance is our goal, we set out to test which angle was most effective in that category. We tested the nail at 6 different angles, forwards and backwards from a 90 degree angle, with three trials for each. We then recorded the change in distance the projectile traveled from each trial. After finding each distance, we took the average distance for each angle. After finding the mean of each, it was clear that 10 degrees backwards was the most effective. To confirm that our data was accurate, we looked to see if our data was consistent and that no outliers altered our data. We then transfered our data into a graph, which showed that the further backwards the nail’s angle is, the farther the distance of the projectile. It also showed that there was a limit to this association too, and that at 15 degrees backwards, the distance was shortened. This again proves that 10 degrees is the perfect angle for our nail, and will result in our nail going the farthest distance. To explain this, we believe that at this angle, the projectile is launched at a 30 degree angle relative to the ground. Theoretically 45 degrees is the optimal angle to include both vertical and horizontal components in flight, but air resistance changes this angle to make around 30 degrees the most successful in distance. This proves that ten degrees backwards is the optimal angle of the firing nail for distance.
- Projectile mass- We started out with a mass of 15 grams and changed it to seven grams. This change was successful, with the ball going almost 9 meters further.
- String Length- Our third improvement was very successful. We changed our 10 cm string to 20cm, with the ball looped around it. This also greatly increased our projectile’s distance
- Shortening of the arm- We shortened the arm of the trebuchet so it was lighter. Making it lighter, which makes it easier to spin. Shortening it also changed the follow through for the projectile.
- Rubber Band Quantity- We increased the amount of rubber bands, to add more force to our trebuchet. This increased the distance of the projectile.
- Rubber Band Length- This adds length, but keeps the same mass. Therefore the force is increased. This was a help to our trebuchet.
- Horizontal Distance- The projectile traveled 25 meters on our most recent trial
- Time in air- The projectile stayed in air for 2.09 seconds
- Horizontal Velocity- 12 m/s
- Vertical Velocity- 1024 m/s
- Total Velocity- 15.74 m/s
- Spring Constant- 81.4 n/m
- Pe spring- The spring had a potential energy of 7.5 J
- KE ball- The ball had a kinetic energy of O.87 J
- Vertical distance- The ball traveled to a height of 5.35m
Reflection
This project was a fun one. My group really collaberated well, and we were very time efficeient. As we improved upon our model, I believe I showed vital leadership in my group. We found the data quickly and we concluded even quicker. Some of the negitives, was that our group worked too fast and the quality of the work was affected. Another negitive is that our group was too confident with our data. We did not check the data enough, resulting in the possibility of more than one vaariable being effected. Next time, I will make sure my group only changes one variable in experimenting. This project was an overall success. I learned a lot about physics and myself.