Fire Away!
Our goal was to create a trebuchet that could fire a projectile as far as possible. The restrictions were such.
- The trebuchet must stay in one place
- Must have two (2) legs that hold up an axle
- A lever with both a load and effort end.
- Must be easily portable, with one person carrying it
- Have no dimension over one (1) meter in length.
- Trebuchet may be set by a person, but not provide the firing.
In our experiment, we made five (5) heights at which our axle could be, they were at 34cm, 30 ½ cm, 26cm, 23cm, and 19cm. When we launched when the axle was 19 cm off the ground, then the projectile went about 1.34 meters. When launched from 23 cm, the projectile went about 1.67 meters. Our other test was at 26 cm, which went about 2 meters.
There is clearly a relationship between the height of the axle and how far the projectile went. These axle height increments were about 4 cm away from each other, and all went ⅓ of a meter farther than the previous launch. So far, this shows that about every 4 centimeters of height increased the launch by ⅓ of a meter.
Our data was normal up until we tested the 30 ½ cm, and the 34 cm. The 30 ½ cm height made the projectile launch about 2.67 meters. The 34 cm launch landed at about 3 meters away from the catapult. We always used 2 rubber bands in our launch, and had the same ball every time,
This shows that there was a jump between 30 ½ cm, and 26 cm. This jump could be due to a thicker stopping bar on our catapult. Every time, except for the 30 ½ cm and 26 cm tests, the projectile landed ⅓ of a meter farther for every 4 centimeter increment. Even after the faulty data, the increments were still increasing by ⅓ a meter. There is reasonable evidence to conclude that there was an error in our data collecting, but there is also evidence that the projectile’s landing distance increased by ⅓ a meter for every 4 centimeters that the axle was raised.
We collected data from other trebuchets that also had changed one variable. We took this data and decided to change our trebuchet, so that we may achieve a farther distance. We made the following changes:
- Remove the basket holding our projectile. Our basket was at a 90° forwards, relative to the lever arm
- Made a 40 cm string that could be made into a sling that held a 10 gram ball
- Add a nail at the top of our lever, pointing at 10° backward, relative to the lever. This adds a point for the sling to attach to
- Added an additional rubber band to make our projectile launch farther
- Removed stopping bar. Research shows, that the stopping bar is hindering our project, for our scale.
Time in air |
1.17 s |
Distance horizontal |
30 m |
Distance vertical |
6.3 m |
Velocity horizontal |
26 m/s |
Velocity vertical |
10 m/s |
Velocity total |
28 m/s |
K |
133 |
PE spring |
10.6 J |
KE |
3.92 J |
Release angle |
28° |
Reflection:
I learned many things while doing this project. I also discovered my positives and negatives that I could improve.
First, the negatives. We had spent too much of our time on trying to figure out which kind of catapult to build, which was a gigantic waste of time. Our other negative was having a teammate be sick for a long time. I could assist by asking the person what they wanted us to do for that day.
Secondly, the positives. We had a lot of good ideas. We had a design for a rat trap powered catapult, or a weight powered one. This helped us engage with our creativity. I also worked with an amazing group which helped generate more ideas to apply to our trebuchet.
This project was the most fun to do, and I loved it.
I learned many things while doing this project. I also discovered my positives and negatives that I could improve.
First, the negatives. We had spent too much of our time on trying to figure out which kind of catapult to build, which was a gigantic waste of time. Our other negative was having a teammate be sick for a long time. I could assist by asking the person what they wanted us to do for that day.
Secondly, the positives. We had a lot of good ideas. We had a design for a rat trap powered catapult, or a weight powered one. This helped us engage with our creativity. I also worked with an amazing group which helped generate more ideas to apply to our trebuchet.
This project was the most fun to do, and I loved it.