So I figured I'd write a blog about my experience in building my first ever catapult! Though it was definitely intimidating at first, I found the project actually turned out to be a lot of fun to build and launch.
My group settled on a trebuchet design, and after working out the ideal angles, sizes and overall plan, we got to building. We built for 2 days, just about 3-4 hours a day. I won't bore you with the cutting and sizing and drilling of wood, because I think we all know that's not exactly the most fun part of the experience. Once we got our catapult mostly built, we began our test trials. Surprisingly, the ball actually went up in the air the first trial! Granted, it was the wrong way...but psh, details.
We did trial after trial, finding minor errors and fixing them; the ropes for the sling were too long, the pouch to put the ball in was too flimsy, the pin didn't stay on long enough or wasn't at the right angle, the throwing arm wasn't totally straight. Now that the preliminary building was over, I actually found it fun to be able to help isolate the different issues with our catapult and figure out how to fix them to make it launch better.
Finally, success....our catapult launched the right way! Tweaking a few more things, we were able to launch a small rubber ball slightly bigger than a softball about 80ft. It was so cool that we had literally just started with some wood, power tools and a design and now we were launching up to 80ft! We decided that was sufficient and left it there, to be launched again that Friday on launch day.
Due to unfavorable conditions (aka LOTS of wind), we had some trouble setting up (and keeping upright) our catapult; however, we still managed to launch 3 trials (though the last one was a bust), our longest distance at 27 yds. Our catapult launched diagonally, however...so if you ask me, I'd say it was longer than 27 yds.
I should probably talk a little about the physics behind the catapult. We put weights on the front of our throwing beam, and when let go the force from the weights brought one side of the beam down and the other side - the side where the sling was attached - up where the softball would release from its pouch. When it released depended on the angle of our pin where the ropes from our sling were attached.
And of course, we all (should) know our kinematics equations. The ball released at a certain horizontal and vertical initial velocity, and by timing how long it was in the air and measuring the distance it travelled horizontally we could figure out these velocities (x = Vot + .5at^2).
Though it wasn't a good day to launch catapults, I still had fun with the project and enjoyed building it and seeing our result. Catapults are pretty awesome.
Until next time,