end of semester 1.1, but mostly rocket lab
I'm back in SPF! The first semester is officially over, save finals in January. Well sort of. I still have my writing seminar paper that's been hanging over my head for ages that I have not yet started for fear of death by boredom. I am definitely going to start it after I finish this entry (if I say it on lj, it must come true!).

In other news, my birthday was on Friday. I had an awesome time skipping (my last) 9AM physics lecture and then spending the hours from 11 AM - 6:30 PM in lab doing analysis on my rocket data. It was death. The problem was too many students who didn't know what to do (myself included) and not enough TAs to go around. The whole format of the lab hours was such a waste of time. However, what we had to do is actually pretty awesome, and I will try to explain it here because obviously it is extremely crucial to everyone's well being. Anyways.

- - - -skip if you do not want to read about physics/rockets- - - -

You might remember a couple of entries ago I mentioned launching my bottle rocket for EMP class. In the rocket was an accelerometer, which, like its name, measures acceleration. We took the data that we got from out rocket launch and graphed it, time versus vertical acceleration. Simple enough. All the time I spent in the lab, though, was for the second part of the lab. We had to recreate the launch data using only known constants (pressure of the gauge, mass of the rocket, length of the launch rod, area of the nozzle, air pressure, you get the picture). So for example, you would use the equation netForce = initialMass * acceleration = initialPressure * nozzleArea - gravity to figure out the initial acceleration, and then assuming that it is the same the whole time the rocket is on the the rod. After it leaves the rod, they tell you that the acceleration doubles (this is a little flakey, but its the only big assumption we make). From there, you can use all the laws of mechanics, rocket equation, drag, Bernoulli's, etc to figure out the pressure, mass, volume, and acceleration of the rocket without ever having to launch it. How the physics just works out is very cool.

So in the end, we plot our theoretical launch data over our experimental launch data, and we (ideally) get a pretty graph. After some tweaking of the initial constants (water mass isn't actually .5 kg because we spilled some, initial gauge pressure isn't actually 70 lbs/sq in because I didn't actually pump it to that level, gamma isn't exactly 1.4 for air because it is made up of many different types of molecules) here is said pretty graph:



I'm a bad person and I did not label my axis. The x is time in seconds and the y is acceleration in meters/second^2. It's not an amazing fit, the theoretical acceleration goes ALOT higher than my experimental data for reason unbeknownst to me, Weihan, Mike, or Sam (our brave grad students who agree to TA this crazy class). But it's still pretty awesome. Yay for applied science!