Our Project
For this project we were assigned to build a trebuchet. It had to be sturdy and very reliable. Additionally, its dimensions had to no larger than one meter and had to portable. We later made modifications to variables in the trebuchet to increase it’s performance. For our trebuchet design we had a large square wood base where are trebuchet would be placed. In the center of the base is where the trebuchet legs are. On both sides of the legs there are planks that act as supports. The axle is made of a long bolt that has spacers on it. The arm is a long wood plank which has a nail sticking out of it that connects to the rubber bands. The rubber bands are on both of the supports and are what makes our trebuchet launch it’s projectile.
Modifications
Clear Paragraph
To maximize distance when firing a trebuchet use a 10g clay ball. In our STEM class we will build a trebuchet and and for projectiles we used clay balls. We were trying to find which ball with which mass goes the farthest. We fired the clay balls and recorded how far they went. We found out that the 10g ball went 8m, the 20g ball went 4m, and the 30g ball when 2m. The 10g ball goes the farthest because it is the lightest so less force is required to move it and it also has the the smallest surface area which means there's less area resistance. This proves that the 10g clay ball goes the farthest due its low mass and little air resistance.
Calculations
For this equation the acceleration is the acceleration due to gravity and the time is how long the projectile fell for.
Initial Spring PE=1/2 (spring constant)(stretch of spring)^2.
Advantages of our Trebuchet
- No arm stopper: We removed the arm stopper from our trebuchet. We did this because not having an arm stopper allows a full motion of the arm which mean there it will have maximum momentum/velocity. In the end mean the projectile will fly farther.
- Spacers: We added spacer on the axle of our trebuchet. We did this so all the potential energy is converted to kinetic energy. When spacers are added on the axle of the trebuchet it helps the arm have less wobble and move straighter. Decreasing the wobble means less energy will be going into moving the arm sideways and more will going moving the arm forward increasing the velocity.
- Mass of projectile: We decreased the mass of the projectile. We did this because having a smaller mass means less energy will be used to accelerate the mass and more would be used to propel the mass forward. Thus increasing the distance.
- Change of nail’s degrees: We bent the nail that connected to the arm 65° forward. We did this because bending the nail to this angle leads to trebuchet releasing the ball at 30° more consistently. Thirty degrees is the most ideal angle to release the projectile at. Since, it decreases the amount of energy converted to vertically distance.
- Thicker and longer rubber bands: We changed the rubber bands we using to be thicker and longer. We did this because thicker and longer rubber bands have more potential than smaller and skinnier rubber bands. Having more potential energy means there will be more kinetic energy. Which will increase the velocity.
- 15cm string nail to ball: We changed the length of the string to 15 cm. We did this because the string we used was longer than 15 cm so the ball would drag on the ground, creating friction and decreasing the momentum that the mass needs to launch.
- Rubber bands vs Weights: We used rubber bands instead of weights for our trebuchet source of energy. We did this because rubber bands have more potential energy than a falling weight. Which means it will move the arm down quicker and the ball will have a higher velocity.
- Lowered axle: We lowered the axle of the trebuchet. We did this because having the axle lowered means the projectile will be fired at a more horizontal angle. When a projectile is fired at a more horizontal angle more energy goes into the horizontal distance resulting in the projectile going farther.
Clear Paragraph
To maximize distance when firing a trebuchet use a 10g clay ball. In our STEM class we will build a trebuchet and and for projectiles we used clay balls. We were trying to find which ball with which mass goes the farthest. We fired the clay balls and recorded how far they went. We found out that the 10g ball went 8m, the 20g ball went 4m, and the 30g ball when 2m. The 10g ball goes the farthest because it is the lightest so less force is required to move it and it also has the the smallest surface area which means there's less area resistance. This proves that the 10g clay ball goes the farthest due its low mass and little air resistance.
Calculations
- Mass of Projectile: 10g or 0.01kg
- Air Time: 1.5 seconds
- Horizontal Distance: 15 meters (49.2 ft)
- Vertical Distance: 11 meters (36 ft)
- Horizontal Velocity: 7.3 m/s (16.3 mph)
- Vertical Velocity: 14.7 m/s (32.9 mph)
For this equation the acceleration is the acceleration due to gravity and the time is how long the projectile fell for.
- Total Velocity: 16.4 m/s (36.7 mph)
- Angle of Release: 30°
- Spring Constant: 122.5 N/m
- Initial Spring Potential Energy: 1.38 Joules
Initial Spring PE=1/2 (spring constant)(stretch of spring)^2.
- Kinetic Energy of the Ball: 0.13 Joules
- Percent of Energy Converted: 9.7%
Advantages of our Trebuchet
- Reliable
- Can easily be modified
- Easy to operate
- The distance where the projectile land is consistent
Reflection
Going into this project was a little weird. Due to being absent form class for several days I was put into a random group and was not able to share my ideas or help in the building process. Despite this I worked well with my team and followed their instruction for what to do for the project. I also worked hard on other aspects of the project to make up for my absence. Even though worked hard and well with my team there were a couple of things I could have done better. I didn't take the roll of being leader during the project, I mostly followed what my team mates said and didn't help my group come to ideas or make any of my own. Additionally, I didn't give much feedback to on my team mates ideas. This project was enjoyable even though I had a rough start and it was short.