Proof of efficacy
Joell Vaca
6/7° Stem
12/8/16
Our goal for this project be to make a reusable catapult that could launch a small mass as far as possible. The rules for this were that no dimension could exceed 1 meter and could not just be a person throwing the mass. The design that we came up with had the axle that the arm spun on 35 cm off the base. The arm was 70cm long and had a 4:3 load to effort ratio. The length and height of the arm helps the projectile travel a farther distance because in a shorter amount of time therefore creating more a higher initial velocity. We had to use lots of rubber bands to give it a higher potential and kinetic energy.
While we were making our catapult we tested the idea of a stopper to make the arm stop at a point in its rotation to send the mass further. Our tests showed that no matter what angle we made the arm stop at the mass still traveled the same distance. For example we made it stop at -18° the mass went approximately 24m and when it stopped at 135° the mass when about 22m. This shows that the mass is already released by the time the arm has come into contact with the device meant to stop it. If the arm is stopped at say 110° it has no difference then if it was stopped at -15° this is caused by the fact that the force on the end of the arm is strong enough to fling the mass off right when it starts. Without the stopper we managed launch the mass at the farthest about 39m in all.
Angle of the release nail
Larger base
Thicker stand
Height of the axle and arm length
Rubber band strength
Stat table
Spring potential energy 9.4 Joules
Velocity Horizontal 17.9 mps or 40.09 mph
Velocity Vertical 20.9 mps or 46.7 mph
Net Velocity 20.9 mps or 46.7 mph
Distance Vertical 5.8 meters or 19.05 feet
Distance Horizontal 39 meters or 127 feet
Kinetic Energy of Projectile 1.7 Joules
6/7° Stem
12/8/16
Our goal for this project be to make a reusable catapult that could launch a small mass as far as possible. The rules for this were that no dimension could exceed 1 meter and could not just be a person throwing the mass. The design that we came up with had the axle that the arm spun on 35 cm off the base. The arm was 70cm long and had a 4:3 load to effort ratio. The length and height of the arm helps the projectile travel a farther distance because in a shorter amount of time therefore creating more a higher initial velocity. We had to use lots of rubber bands to give it a higher potential and kinetic energy.
While we were making our catapult we tested the idea of a stopper to make the arm stop at a point in its rotation to send the mass further. Our tests showed that no matter what angle we made the arm stop at the mass still traveled the same distance. For example we made it stop at -18° the mass went approximately 24m and when it stopped at 135° the mass when about 22m. This shows that the mass is already released by the time the arm has come into contact with the device meant to stop it. If the arm is stopped at say 110° it has no difference then if it was stopped at -15° this is caused by the fact that the force on the end of the arm is strong enough to fling the mass off right when it starts. Without the stopper we managed launch the mass at the farthest about 39m in all.
Angle of the release nail
- We decided to make the nail that the mass hung off of at a 35°-45° angle therefore making the release point higher in the air so that the projectile traveled farther.
Larger base
- We made the base that the stands were on wider so that the catapult was more stable and durable.
Thicker stand
- We choose to use 2” by 4”s to make it more sturdy and less likely to crack or break.
Height of the axle and arm length
- To get a bigger rotation we razed the axle and extended the arm making the arc that the arm travels larger.
Rubber band strength
- We only used 4 rubber bands to propel the arm around faster without putting too much pressure on it resulting on a split in the wook.
Stat table
Spring potential energy 9.4 Joules
Velocity Horizontal 17.9 mps or 40.09 mph
Velocity Vertical 20.9 mps or 46.7 mph
Net Velocity 20.9 mps or 46.7 mph
Distance Vertical 5.8 meters or 19.05 feet
Distance Horizontal 39 meters or 127 feet
Kinetic Energy of Projectile 1.7 Joules
Reflection
In reflection This project was different from all of the others because our first prototype was much more powerful and fired our projectile much farther than our end product. As we continued testing it the arm started to split down the middle and the legs broke off at the nails. Even though our first projeect fell apart we worked well as a group and we quikly made one more version of they catapult which can be seen in the slide show at the top of this page. After making this veersion it didn't fire as far but would still work to get the numbers that we needed.