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Rshadler

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  1. Rshadler

    AP Physics C Midterm

    By Rshadler,

    Ok, so today is my midterm and I've been studying and looking over my notes and everything and I think I'm about ready. The test is going to be an actual AP Mechanics exam I guess, so I've done a few practice ones and such to get ready for it. I'm hoping that I can get at least a 4 on this thing. This going to be a short post for now but I plan to update this later after the exam so I can complain talk about it. I guess that's all I have to say for now.



    Wish me luck!



    OK, that's one exam down! I think the multiple choice was a little rough (and by rough I mean there some questions that I completely guessed on because I had no clue) BUT I think the free response went better. There was a question on certain topic I hadn't studied (it was air resistance) so now I know what to study next time. Turns out I knew a lot more than I thought I did about mechanics! All in all, great learning experience!



    Thanks for stopping by!
  2. Rshadler
    The throwing saga continues! This post is all about shot put (the one that looks like throwing a cannonball), my other event. In this a event, throwers compete to see who can launch a weighted metal ball (8 lbs for girls, 12 lbs for guys) the farthest distance. This fairly basic projectile motion, but a lot of people struggle with it. So, here goes:



    Actually, I lied. This is slightly more complex projectile motion since, as the diagram shows, the release point in a height (h) off of the ground (not on the ground) which changes out equations quite a bit. However, we know the equation of a projectile in free flight:



    So this is very helpful. Now, we want to figure out the angle the will create the maximum distance. A basic knowledge of physics and/or trig will tell us 45 degrees should be the optimum angle of projection. Any higher or shorter and the distance begins to shrink. The following data certainly agrees with that assertion:



    If the optimum is around 45 degrees and we know this, why is it so hard for us to throw an 8 lb ball a good distance. A lot of throwers have the issue of completely removing the angle of projection altogether. In doing so, they release straightforward and the distance travelled by the shot is dramatically decreased. The lack of angle is due mostly to the inability of arm muscles to support a shot put (although that means they're holding it wrong).

    So what does shot put actually look like?



    Ok, not that fast, but you get the idea.

    For more info, check out Http://www.people.brunel.ac.uk/~spstnpl/BiomechanicsAthletics/shotput.htm
    (this where I got the data and the diagrams!)

    That's all I've got! Thanks for checking this out!
  3. Rshadler
    Hello again! As you might have guessed this post is not about a TV Show (though I could probably find a movie or show that involves what I'm going to talk about). I actually want to talk about the physics behind throwing a discus. The discus throw is one of the events I compete in with the school track team, so in honor of our first meet yesterday I decided to do a blog post on it. A "disc" or discus looks like this:



    The larger radii are for men while the smaller, lighter discus are for women. First things first: how does one throw a disc? The most important part of throwing a disc is releasing it in a way that creates back spin. The spinning motion stabilizes the discus in flight. The faster the disc spins as it leaves the hand of the thrower, the greater the angular momentum and the more stable the flight. This keeps the disc from wobbling and tilting on its axis as it flies, helping to maintain lift which prolongs flight time. This is called gyroscopic stability. The goal of this sport- of course- is to throw the farthest so the longer the flight time, the better.

    I can't find a good image to show you, but the disc is shaped similarly to the wings of an airplane. Due to this shape, the disc gains lift due to increasing wind speed, helping the disc to travel further in windy conditions. That does not mean that wind is necessarily good for a discus throwing, in fact the even is cancelled (at least at the high school level) in high winds. The discs are affected by wind speed and direction (the greater lift comes from the speed of the air moving around the disc) and they're very light (1 kg for a girls disc) and thus strong winds in any direction to the right or left of movement of the disc can push it off course a rather large and scary distance, which can injure spectators or runners on the track. This happened at a meet last year, luckily our runner out ran the falling disc and she never noticed until after her race that the disc had nearly hit her. Interestingly though, a headwind- a wind directly opposing the disc- can actual add up to 25 ft of distance (as opposed to wind in the direction of the disc's movement. This has to due with the combination of aerodynamic lift and gyroscopic stability.

    So, that's a quick, basic look at the discus throw. There are tons of cool videos and explanations online that get even more in depth into how the sport looks, in case you want to learn more.

    If you're wondering about the title, I've had one too many people say something like "Oh, you mean you throw it like a Frisbee right?". No, I do not throw it like a Frisbee. That would not be safe.



    That's all I have. Thank you for taking the time to read this!
  4. Rshadler
    So I've realized that with all the posts I've done on Doctor Who, I never actually looked at the theory behind how the T.A.R.D.I.S. can actually travel through time. There have actually been studies into how a time-travelling space might work in this universe and the findings have led physicists to believe it is theoretically possible for a T.A.R.D.I.S. to exist and to function as it does on the show in our universe.

    The research paper is called Traversable Achronal Retrograde Domains In Spacetime (see what they did there?) and it was written by a pair of physicists named Ben Tippet and David Tsang. Tippet and Tsang proposed a spacetime geometry in which retrograde time travel, travelling back and forth along one's own timeline, is possible. A spacetime geometry is when spacetime- the fabric of the universe (where everything has happened, happens, and will happen in the future)- is arranged in a certain pattern. This is a fairly complex topic; however to put it simply, space exists of three dimensions (X,Y,Z) and time creates a fourth dimension. There are many theories as to how this spacetime geometry might be structured- the most famous being the Euclidean and Minkowski space.

    In order for retrograde time travel to be possible, spacetime geometry must be structured in a way such that the time dimension curves around and back in on itself. This spacetime structure- called closed timelike curve or CTC- would theoretically allow one to hop from their current space and time to another space and time (i.e. the idea of the "time votex"- basically a wormhole- that the T.A.R.D.I.S. flies through). Essentially the T.A.R.D.I.S. would create its own sort of bubble containing a closed timelike curve, which it would use to travel through time and space.

    So that's essentially what the universe would have to look like for the T.A.R.D.I.S. to exist. Given the vastness of the universe and how long it has and will exist, there actually is a possible these conditions already exist somewhere and that a race like the Timelords already exists out there too.

    So that's about it, thanks for taking the time to read this. If you're interesting in learn more you can find Traversal Achronal Retrograde Domains In Timespace by Tippet and Tsang or you can check The Blue Box White Paper, which takes a more basic approach to the concept; both of these papers should be online if you search for the title.
  5. Rshadler
    It seems fitting to close out my tenth and final blog for the first quarter by talking about the season finale of the 8th season of Doctor Who.

    In this episode the Twelve Doctor gets thrown out of moving plane and yet he still manages to call his T.A.R.D.I.S. in mid-fall. The Doctor would have been falling at a fairly quick rate, he would have been in free fall. Obviously, since he is able to catch up to the T.A.R.D.I.S., the T.A.R.D.I.S. is moving at a smaller speed. That would explain the fact that he can catch up the T.A.R.D.I.S. but it still does not mean he can get the key in the lock and turn. First of all, he would crash into the T.A.R.D.I.S. quite hard- given the speed differential- rather than float next to it. For this to be avoided the T.A.R.D.I.S. needed to speed up (its not like the Doctor can really slow himself down) quite significantly and yet there are no changes to T.A.R.D.I.S. at all while its in flight. Somehow though, it slows down enough for the Doctor to slide the key in and get inside. But where would he go once he is inside? He still be moving at the speed he was prior, except now in a confined space. Perhaps the T.A.R.D.I.S. upped the gravity inside the itself in order to slow him down or maybe he managed to land in the swimming pool. One thing is for sure, the writers are once again stretching the boundaries of physics.

    Ok so this is really short with no visuals because I cannot find any yet (I really wish I could). I'll edit this again later.

    Edit: I found a video clip of what I'm talking about. You can click the play button below to watch it. http://www.youtube.com/watch?v=QbdjmCa1N4I.

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