# Swagmeister11

Members

20

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• Birthday 01/11/1994

## core_pfieldgroups_99

• Interests
Running, Learning, Edumacating, Reading, Skiing, Math, and Phyzics

10

1. ## Differential Equations Have Some Swag After All

So I'm actually in my honors chemistry class right now, but who cares right? It's not like it's physics... anyways, good to be back! Yesterday, in my differential equations class, we started section 2.3-- I don't actually remember the title-- at the ungodly early hour of 9 AM. aka, really not that early. Now, if I/ other AP C past/current students remember correctly, early in the year we discussed air resistance on a falling object. According to Newton's 2nd Law, net force or ma equals whatever you determine to be the net force. In this case, using a force diagram, you have the force of mg down minus the effect of air resistance (I'll use kv in this case because we used it in my math class, though last year we used bv and cv^2 I believe). Thus you have ma=mg-kv, and since a=dv/dt, you have m(dv/dt)=mg-kv . This is (wait for it) a differential equation! Yay! Specifically, it is a linear differential equation, more commonly seen in the form dv/dt+ (something)*v=something. So when Mr. F just skipped over the steps/integration/nothing made sense, that's why. It was a DE. Note: I don't fully remember how we did the problem, but I think we were just told what the equation came out to, and skipped the actual steps. Anyways, you put it into the form dv/dt+(k/m)*v=g (the dv/dt can't have a coefficient), and then you do a bunch of really really really cool steps to solve it. You take the stuff in front of the v (in this case, k/m) and set up this: e^(integral of k/m dt). Clearly, this gives you e^(kt/m). You then multiply everything in the equation by this, giving you (e^kt/m)*(dv/dt+ (k/m)*v) = g*(e^(kt/m)). The left side of the equation turns into d/dt of e^(kt/m) times v. We don't actually do anything to get to this, it's just known that that's what it turns into, and you can check it to make sure. You know have d/dt of e^(kt/m)*v = g*e^(kt/m). you integrate both sides with respect to t, leaving you with: e^(kt/m)*v=e^(kt/m)*gm/k + Constant ©. Then just isolate velocity. That gives you v(t) equals gm/k+ C*e^(-kt/m), and you can solve for C pretty easily (either with v(0)=v(subscript)0 or v(0)=0. And that's your air resistance equation! (hopefully) I'm assuming I messed up a negative sign somewhere, or it should be -gm/k, or something else, but that's the general shape of a) a Linear DE and this force equation. Hopefully it's mostly right, and not overly boring because it's actually kinda cool. So yeah... go physics! Probably the longest blog post I've done, but I deemed in necessary. Sincerely, your resident Swagmeister #APC Rules
2. ## Nick, Tim, and Eric's Magnetic Leviation Project

For our end of the year project we chose to do magnetic levitation (not the smartest choice in retrospect). There are usually two ways to do this. One is to run an electric current and create a magnetic field so the platform and the track repel, and another is to just use bar magnets (as the track and attached to the platform) which will repel each other if the poles are simply set correctly. We chose to do the latter, as it spares us from doing any RHR or actual physics like that. We tried (I believe) 3 designs, each using 3 of the same size pieces of wood as walls and a floor for the track. Our first attempt at the track was to take eight bar magnets and lay them horizontally across our approximately 3 inch wide track (magnet's length is 2 inch, width is one, so we laid them lengthwise like | | | | etc. Since they attract each other like that though, to hold them in place we used flathead screws to pin them down. We also put little disc magnets (not as strong, two of each) between each set of bar magnets for better repulsion. This idea did not work, however, as the only flathead screws we could find had metal in it, and thus would become magnetized and actually attract our platform (which, until the end, was just cardboard with a single bar magnet on top). So the platform would be repelled by the magnets but attracted by the screws, and did not work at all. So we took out the screws and just taped everything down. This also did not work, since the magnet on our platform was attracted by the edges of the magnets (essentially the same problem as with the screws). We then took the tape and all the magnets off, then turned the magnets so they followed the track like - - - - - -. This reduced the problem of attraction, and adding the little disc magnets in between the bar magnets reduced it further (track looked like -o-o-o-o-o- except the o's are smaller...). Unfortunately, Nick and I could not, at the time, figure out a way to reduce tipping/attraction to the track. Luckily, this is where Tim came in (and Nick too, I know he wants credit, and I don't really deserve any since I was writing the letter at the time). Instead of just one magnet on the platform, he took two and arranged them on either end of a rectangular platform (with a cutout in the middle to reduce weight). This solved not only the tipping (simply by sheer counterweight), but also the attraction of the platform to the track (for, if you can picture it, when one magnet is attracted to the track, the position of the other one is such that it will balance the force). He also added tape on the walls to help it glide easier, and with that the project was finished. Cleanest, neatest project? No. Effective (in the end)? I would say so. I realize that this is hard to visualize, but I don't have a picture so this is the best I could do. Anyway a great way to end a year of Physics C!
3. ## Free Swag. Not Speech. Swag.

Your Swagmeister himself found this a few weeks ago: http://news.yahoo.com/blogs/technology-blog/weird-gun-future-attacks-words-not-people-193050045.html It seems some of the more savvy (or most frustrated with with loud teenage conversations) scientists in the world have developed a silent gun prototype. Not a gun that makes no noise, but one that prevents people from speaking, through a combination of biology/neurology(?) and naturally physics. By playing back their own voice on delay, the gun confuses the speaker-- not that several people (who will remain nameless) aren't already confused...-- and essentially prevents them from talking further. The science behind this is more biological in nature, but it is still physics that determines what the wavelength and direction of the replayed sound must be. But while the science is interesting, but the repercussions are disconcerting. Though this gun could be used to quiet a library or, per say, keep a class of AP C students silent, it could also completely inhibit free speech, one of the biggest parts of American democracy, which I for one would like to keep. Otherwise my swag is extremely limited, which is not allowed at any point in time. So yay physics, but nay physics... p.s. *could be used on a mister souf* *cough*
4. ## Swagitance

One note before I begin my wonderfully edumacative blog: Swagitance is like capacitance, except it measures swag in high-schoolers (units are still farads cuz that word's cool) Anyways, capacitance. More specifically, circuits involving them. According to I-Town's resident electrical engineer (room# 3012), all those capacitor only circuits are practically wrong. Since V=IR, if there is no resistor, current is infinite and everythang would blow up (ie a calculator). Thus everything we had learned was a lie. which is semi-annoying... However when resistors are added, things get much more interesting, and realistic. When the circuit is first established, at time=0, the capacitor, as it is empty, acts like a wire, and current flows through it (I=max I) and Voltage (across capacitor)=0. However, as time goes on and the capacitor fills with charge, it limits the current flow across it, decreasing current but increasing voltage. Thus as time approaches infinity, current approaches zero while voltage approaches that of the voltage of the battery (asymptotic behavior), and the capacitor acts like a switch that has been opened creating a open circuit. As to why this happens, it's in the textbook. read it. may have something to do with the allignment of molecules? not sure, as I need to actually read 25.4-.6 tonight... aka peace ya'll (in southern drawl)

1946 you amateur
6. ## Swag Dodgeball

So friendz I felt I should enlighten you on another one of my infinite talents. It involves throwing, and avoiding, numerous spherical objects, coated with a 'gator-like' material. Namely dodgeball. Now dodgeball is only enjoyable when you win, so needless to say I find it very appealing. However that's besides the point. There are numerous physics applications to dodgeball. One such thing is throwing the ball itself. Naturally most people know where they want to throw it... it just rarely ends up there. That's because many of them are uneducated on the art of physics. When many people throw a dodgeball, they accidentally put a spin on it, either spinning away from you, towards you, left, or right-- all depending on how your fingers release the ball. This spinning action creates a effect that Bernoulli discovered; the ball creates a difference in air pressure, caused by the different wind/air speeds on opposite sides of the ball. The side with lower pressure is the side that the ball spins towards. With this knowledge, smart players can trick the opposition, as long as the have control over the spin-- you don't want to let the ball float. Obviously this concept is a pivotal part of baseball too, but dodgeball is so much cooler... pc
7. ## Wind Vectors

smashed by two seconds is not smashed. Now if it was by over two minutes, THAT would be smashed... Oh wait that's what happened (Geoffrey Mutai, 2:05:06). PROOF-READ
8. ## Independent Study? Swag.

S'up everyone who is reading this (so basically my fellow classmates who are under orders to) and welcome to another blog post from the one, the only, Swagmeister. This weeks post includes a video! How exciting! And some physics... the link is: http://www.youtube.com/watch?v=MO-BmG8kooA It contains the entire highlight of the bills patriots game on September 25th, but the part I am concerned with is the end of video where Lindell makes the game-winning field goal. This is a perfect (or at least decent real-life example) of impulse and momentum and their relationship, known as the impulse-momentum theorem. This theorem states that Impulse (J)= Change in Momentum (delta p), or since J= Force times time and p= mass times velocity, Ft=m(delta v), Ft= delta p, etc... Anyways this theorem is illustrated in the process of kicking a field goal because: the ball is initially at rest, thus it's momentum is 0. To change its momentum, an impulse must be applied to it. It is this impulse that will create the velocity of that football as it sails through the air, beating those stupid patriots. This impulse is created by the kicker applying a force on the ball (with their leg/body of course) for a time t. This is why follow through is so important, because it increases the time for which the force is applied and increases the impulse, causing a bigger change in velocity. Though, as Scott Norwood can tell you, having a big enough impulse does not guarantee that you will make the field goal... Enough on sad topics like wide right, for I've got a bills game to watch. Peace, my band of physics brotherz
9. ## Swagitect

S'up World. Let's get right to it... So while building a trebuchet (not a catapult), I learned several important things: a) I'm not much of a carpenter... or one at all. I clearly need to by one of those hands-off, not hands-on kind of scientists serious trebuchets take more time to build then one thinks, but surprisingly less money than i thought (not that i was paying for it) c) Physics of it (specifically on the main beam, ignoring the mass of the beam): Our counterweight consisted of 125 pounds of weights, which is approx. 57 kg or (in weight/force) 570 Newtons. This force was multiplied by the distance to fulcrum (in our case a rod), which was significantly shorter on the counterweight side than the other side. Due to the lack of weight on the other end of the beam (even though the length was longer), there was a net torque (Torque=F cross L) in the counterclockwise direction, causing the beam to move CCW, accelerating the ball at the long end of the beam and flinging it off into the darkening Rochester sky... when it worked right. Though to be honest, I'm not entirely sure why the throwing section of the beam should be longer, because wouldn't it generate a the same torque but a bigger force if it was closer? unless the length is only included so you can launch at a greater height... Anyways cool experience for the Swagmeister, I'll see you all on the the battlefield of physics
10. ## Physics With Swag

I, as supreme emperor of the universe, have decided that this week's post will be dedicated to revealing one (of many) of my physics flaws... such as Newton's 3rd law. Well not exactly the third law, but applications of it. Ie the problems where you have blocks next to each other, a Force F pushes on one block and you have to find the force of Block 2 one Block 1, etc... For some reason, I could never get these right, which, to put it mildly, was really annoying. Especially since I could get the ones with strings in between them. Anyways, I seem to have figured out my problem (at least I hope so). Thanks to this week's lessons on dynamics, I have discovered that in these cases, the acceleration of all the blocks will be the same, so if they are different masses, so will the forces (Right? Please tell me that's correct...). To be honest, I'm not entirely sure why I didn't figure this out sooner, but (if it's correct) it should make dynamics easier for moi. Either way, I like the fact that we're learning about drag, cause it applies a lot to running, so maybe we can go more in depth in class if we have time? Awesome. Swag Out.
11. ## Physics of a Push-up

1) To do correct pushups, one must lift their entire body off the ground, not just their shoulders (aka daoss pushups look like / ) 2) Yeah don't forget work and power teh N00bz