Machine Descriptions:
Modifications:We changed our original ball to a 10 g ball.
- It improved the distance that the projectile went because when it was too heavy it wouldn’t go as far.
We changed the length of the string attached to the ball.
- When we had a short string it had little to no impact on the machine and did nothing for us, but when we lengthened it the projectile went further. We tested a variation of different lengths, but we decided on a 15 centimeter long piece of string. It gave us our maximum distance of 8m, which isn’t a lot, but it’s better than 2m which it went before we had the longer piece of string.
We improved the sturdiness of the legs.
- The legs on our machine were very wobbly and didn’t do us much good. In fact, our machine didn’t work at all without steading the legs. Once we did that, our machine started to work better.
We used six tied rubber bands.
- Originally, we had 5 stretched out rubber bands that weren’t tied, but then we decided to try and tie them for double the strength. We decided to add another one so when we were launching the projectile it had more force.
We made the hole smaller for the pipe to go into.
- When the holes were larger, it was harder for the pipe to stay in one place so we tried some different sizes and the size we used was the best hole we could do. It improved the structure of our trebuchet.
We moved the pipe to the middle of the arm.
- When we had the pipe on the ends of the arms the ball usually flinged back, rather than it going forward. Once we moved it, it didn’t go behind us as much even though it did still happen sometimes.
We added an arm stopper.
- Before we had the arm stopper it kept flying back or going 1m in front of our machine. When we got the arm stopper it immediately went forward.
We added a nail to the end of our base.
- Since we had rubber bands, we had to attach them to something, so we added a nail to the end of our base so nails had enough room to stretch to increase the force of the projectile increasing the distance.
My CLEAR paragraph:
Our claim for our Fire Away project is that 6 tied, large rubber bands on a nail launch the ball from the trebuchet only when the arms are stable. Just like everyone else in our class our trebuchet has two legs, a base, and one arm. Figuring out how to launch it and get it far is up to you. Our group couldn’t seem to figure out the leg base, so we tried many ways to get it completely stable so our project will work. A pretty obvious, but necessary piece of evidence is that with the leg stability it actually works and the farthest point our ball launched is 8m. When the legs weren’t stable it went 0m because it was un-launchable. What our evidence shows that with arm stability our machine works and without it, it doesn’t. The reason for this is that when you attach the rubber bands with no stability they just collapse. The reason why is that there is no potential energy stored so it just clashes down.
Calculations:
Horizontal Distance: The farthest the ball traveled was 8 meters which is equal to about 26 feet. There were meters checked on the ground so that’s how we figured out the distance.
Time in Air: The time the ball was in the air was 1.7 seconds. The time it was going up was 0.85 seconds, then going down was also 0.85 seconds. We figured that out by timing the time from when it launched to when it hit the ground. Then we divided it by 2 to find the time up and down.
Vertical Distance: The vertical distance was 3.54 m/s. We figured that out by using the equation ½ at ^2.
Horizontal Velocity: The horizontal velocity was 4.7 m/s. We figured that out by using the equation d/t (distance divided by time). We used our horizontal distance (8m) and divided that by our total time (1.7s).
Vertical Velocity: The vertical velocity was 8.3 m/s. We figured that out by using the equation a/t (acceleration divided by time). We used the acceleration of 9.8 m/s and divided that by our time up (0.85 s).
Total Velocity: Our total velocity was 90.98 m/s. We figured that out by using the Pythagorean Theorem (a^2+b^2=c^2). We squared our horizontal and vertical velocities and we added them together to get the total velocity.
Spring Constant: Our spring constant was 12.25 N because we used the force from our machine divided by our horizontal distance (98/8) which is 12.25.
Initial Spring Potential Energy: Our initial spring potential energy was 4802 N. We figured that out by using the equation (PE Spring = ½ k x^2).
Kinetic Energy of the Ball: 41,386. We figured that out by using the equation ½ m v^2.
Percent Energy Converted: 1. Because the potential energy and the kinetic energy are the same thing, the answer must be one.
Main selling points of our machine:
- Our machine has a 31x9x4 cm wooden base. It has two 34x9x4 cm wooden legs. There is one 67.5x4x4 cm wooden arm and one 39x3 cm pipe. There are three nails with large heads and six tied rubber bands. On the pipe there is a small piece of clay surrounding the circumference of it to steady the pipe making the projectile launch farther.
Modifications:We changed our original ball to a 10 g ball.
- It improved the distance that the projectile went because when it was too heavy it wouldn’t go as far.
We changed the length of the string attached to the ball.
- When we had a short string it had little to no impact on the machine and did nothing for us, but when we lengthened it the projectile went further. We tested a variation of different lengths, but we decided on a 15 centimeter long piece of string. It gave us our maximum distance of 8m, which isn’t a lot, but it’s better than 2m which it went before we had the longer piece of string.
We improved the sturdiness of the legs.
- The legs on our machine were very wobbly and didn’t do us much good. In fact, our machine didn’t work at all without steading the legs. Once we did that, our machine started to work better.
We used six tied rubber bands.
- Originally, we had 5 stretched out rubber bands that weren’t tied, but then we decided to try and tie them for double the strength. We decided to add another one so when we were launching the projectile it had more force.
We made the hole smaller for the pipe to go into.
- When the holes were larger, it was harder for the pipe to stay in one place so we tried some different sizes and the size we used was the best hole we could do. It improved the structure of our trebuchet.
We moved the pipe to the middle of the arm.
- When we had the pipe on the ends of the arms the ball usually flinged back, rather than it going forward. Once we moved it, it didn’t go behind us as much even though it did still happen sometimes.
We added an arm stopper.
- Before we had the arm stopper it kept flying back or going 1m in front of our machine. When we got the arm stopper it immediately went forward.
We added a nail to the end of our base.
- Since we had rubber bands, we had to attach them to something, so we added a nail to the end of our base so nails had enough room to stretch to increase the force of the projectile increasing the distance.
My CLEAR paragraph:
Our claim for our Fire Away project is that 6 tied, large rubber bands on a nail launch the ball from the trebuchet only when the arms are stable. Just like everyone else in our class our trebuchet has two legs, a base, and one arm. Figuring out how to launch it and get it far is up to you. Our group couldn’t seem to figure out the leg base, so we tried many ways to get it completely stable so our project will work. A pretty obvious, but necessary piece of evidence is that with the leg stability it actually works and the farthest point our ball launched is 8m. When the legs weren’t stable it went 0m because it was un-launchable. What our evidence shows that with arm stability our machine works and without it, it doesn’t. The reason for this is that when you attach the rubber bands with no stability they just collapse. The reason why is that there is no potential energy stored so it just clashes down.
Calculations:
Horizontal Distance: The farthest the ball traveled was 8 meters which is equal to about 26 feet. There were meters checked on the ground so that’s how we figured out the distance.
Time in Air: The time the ball was in the air was 1.7 seconds. The time it was going up was 0.85 seconds, then going down was also 0.85 seconds. We figured that out by timing the time from when it launched to when it hit the ground. Then we divided it by 2 to find the time up and down.
Vertical Distance: The vertical distance was 3.54 m/s. We figured that out by using the equation ½ at ^2.
Horizontal Velocity: The horizontal velocity was 4.7 m/s. We figured that out by using the equation d/t (distance divided by time). We used our horizontal distance (8m) and divided that by our total time (1.7s).
Vertical Velocity: The vertical velocity was 8.3 m/s. We figured that out by using the equation a/t (acceleration divided by time). We used the acceleration of 9.8 m/s and divided that by our time up (0.85 s).
Total Velocity: Our total velocity was 90.98 m/s. We figured that out by using the Pythagorean Theorem (a^2+b^2=c^2). We squared our horizontal and vertical velocities and we added them together to get the total velocity.
Spring Constant: Our spring constant was 12.25 N because we used the force from our machine divided by our horizontal distance (98/8) which is 12.25.
Initial Spring Potential Energy: Our initial spring potential energy was 4802 N. We figured that out by using the equation (PE Spring = ½ k x^2).
Kinetic Energy of the Ball: 41,386. We figured that out by using the equation ½ m v^2.
Percent Energy Converted: 1. Because the potential energy and the kinetic energy are the same thing, the answer must be one.
Main selling points of our machine:
- Very easy to figure out; not a complicated design
- It doesn’t fire far, but it’s adjustable
overview
We were given 2 weeks to build a catapult or trebuchet. It's supposed to have a base, two legs, and an arm. The goal was to launch a ball as far as possible. Ours went 8m, which isn't that far but it works! Not only should the machine work, but it should be reusable.
Reflection
I had an interesting group for this project. I had two of my really good friends Peter and Chase. Some things that were good with this group was that they helped me with the power tools and I kept them on track. Some bad things though were that we had terrible time management. Also, some days there would only be one person or two people working and I feel we definitely could've improved that. But in the end, our machine worked and we had a good time building it.