Kellen+and+Kristyn's+Trebuchet

 __** Build a Trebuchet -- Physics 30 Project **__ ** __Applied Physics Principles:__ **

Projectile Motion -- Projectile Motion refers to an object which is shot into the air. We can use our knowledge of projectile motion, such as the principles of trajectory, to help us improve our trebuchet's efficiency.

Newton's 2nd Law -- Force equals mass times acceleration. We can use this to figure out how much force our trebuchet will create based on how heavy it is and how fast the counter-weight accelerates the throwing arm.

Gravity -- The force that pulls objects to the ground. It is very important because if there was no gravity, the projectile would keep flying and never stop, therefore always missing the target. Also, because the acceleration of gravity is constant, we can calculate how far the projectile will travel before it reaches the ground.

Kinematics -- The study of motion.


 * __Building Procedure:__**


 * 1) Create a basic design/outline for the trebuchet
 * 2) Make an exact blueprint for the trebuchet
 * 3) Gather required materials
 * 4) Cut pieces of wood to specified lengths and widths
 * 5) Drill required holes
 * 6) Attach support arms to base
 * 7) Attach triangular side supports to base and support arms
 * 8) Glue the ammunition holder onto the end of the swinging arm
 * 9) Place bolt sleeves around 6" bolt
 * 10) Put bolt through the hole in the throwing arm to create axel/pivot point
 * 11) Put bolt through the two support arms (with swinging arm and bolt sleeves in the middle)
 * 12) Attach nut to the end of the bolt to hold bolt in place
 * 13) Put string through hole on the throwing arm (side that doesn't have the ammunition holder)
 * 14) Attach counterweight to the string


 * __Materials:__**
 * base - 30" long and 6" wide
 * 2 supporting arms - 20" high, 2.5" wide, 0.75" thick
 * 2 triangular side supports - 8" high by 6" wide
 * throwing arm - 32" long, should be lighter if possible so it can accelerate faster
 * one very small strainer (ammunition holder)
 * pennies and carabiners for the counterweight
 * ziploc bag to hold the counterweight
 * lots of string
 * hot glue gun
 * deck screws
 * power drill with various drill bits
 * one 6" bolt
 * nut
 * several things may be used as "bolt sleeves" to stop the throwing arm from moving back and forth
 * powersaw
 * ruler with a machinist square attached
 * measuring tape




 * __Testing Procedure:__**

The first test was done without a ball to lauch to ensure everything was working. We then started testing our trebuchet using a small, light ball. We quickly realized our trebuchet did not launch far enough based on its weight and arm length and tried several different tweaks such as different counterweights, different arm lengths and weights, and even tying up the counterweight at different heights relative to the throwing arm.


 * __Test Results:__**


 * Trial || Mass (kg) || Arm Length (m) || Distance (m) || P=D/ML ||
 * 1 || 3.63 || 0.7 || 2.65 || 1.04 ||
 * 2 || 3.63 || 0.7 || 2.64 || 1.03 ||
 * 3 || 3.63 || 0.7 || 2.95 || 1.16 ||
 * 4 || 3.63 || 0.7 || 2.95 || 1.16 ||
 * 5 || 3.63 || 0.7 || 2.64 || 1.02 ||
 * 6 || 3.4 || 0.89 || 2.77 || 0.91 ||
 * 7 || 3.4 || 0.89 || 3.09 || 1.02 ||
 * 8 || 3.4 || 0.89 || 3.21 || 1.06 ||
 * 9 || 3.4 || 0.89 || 3.28 || 1.08 ||
 * 10 || 6.35 || 0.89 || 6.38 || 1.13 ||
 * 11 || 5.67 || 0.89 || 6.19 || 1.23 ||

There are a few errors in these results. We did not measure the length of the arm to the end of the counterweight, we only measured it to the end of the piece of wood. Therefore all the arm lengths would actually be slightly longer than the lengths presented in the data table if the measurements had been taken correctly. Unfortunately that makes our tests slightly inaccurate but it still allowed us to compare the results from our different tweaks to see which was best.

On another note, while we were testing we ran out of room on the sheet and didn't make another table. We continued to make adjustments to our counterweight and arm length so we do not have all the test results shown. Our final trebuchet was tested but the results were not recorded.


 * __Analysis of Tweaks to Trebuchet:__**

The first tweak we made to our trebuchet was to increase the length of the throwing arm. We knew that would make it throw farther, and we got a lighter piece of wood so that our new throwing arm was the same weight as our original throwing arm. It ended up improving our trebuchet because the added distance outweighed the extra length of the arm.

Next we decided to increase how heavy our counterweight was so we could increase the acceleration to hopefully increase the distance. We took part of a trailer hitch and tied it to our trebuchet. It was really heavy so it did increase the distance, but it was also really long and added quite a bit of length to our throwing arm. Also, in hindsight, it would move our entire trebuchet a few centimeters when it fired so it may have been almost "too heavy" for our trebuchet.

Then we decided to tie the counterweight closer to the end of the throwing arm to see if that would somehow increase the distance. Turns out, it decreased the distance. When we tried to move it back to how it was before, we couldn't quite get it. The distance just would not get back to what it used to be. It must've been a fluke because we think the counterweight would touch the base when it came down, decelerating it thus shooting the ball sooner and at a more optimal angle. We couldn't find that spot again and since that counterweight was so heavy, we decided to scrap that one altogether.

We wanted a heavier weight than just a bag of pennies for our counterweight, but the piece of the trailer hitch didn't work. After much panicking and stress over what to use, we just found some metal carabiners laying around the house and decided to add those to the bag. It added the little bit of weight that we needed, without adding any extra length to the throwing arm and the launch distance was fairly good so we chose to use that counterweight.

If we were to do this project again. We would most likely make our trebuchet much smaller and lighter. From what we observed at the launch session, the trebuchets that were smaller were much more successful because they were lighter and their swinging arms were much shorter and those each play a significant factor in the P=D/ML equation.