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oxy126

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  1. oxy126
    The gravitational two-body problem is a popular concept in the study of planetary bodies. In essence, it models the paths taken by two massive objects orbiting around each other. Earlier today, I was thinking about our Earth's orbit around the sun, and how while it is easy to think that the Earth doesn't move the sun, it does. So while our solar system surely doesn't have only two bodies, I decided to assume it did (and with a perfectly circular orbit), and calculate just what the orbital radius of the sun is.

    Beginning this, I actually had no idea the gravitational two-body conundrum existed, so I tried to solve for part of it myself. Knowing the force of gravity on both objects (Gm1m2/r^2), and the centripetal force necessary to maintain said orbits (mv^2/r - note, however, that the r in both equations is not the same: the r for gravity is the sum of the radius of both bodies around the barycenter, or center of the orbit). Using this knowledge (and I won't bore you with the steps), I arrived at Ea/w^2 = Sb/v^2, with E=mass of earth, a=distance from Earth to barycenter, w=velocity of the sun, S=mass of sun, b=distance from sun to barycenter, and v=velocity of the Earth. However, I felt this required too many known values, and could be simplified.
    From there I looked into the laws of momentum. Knowing that the force of gravity was the same on both bodies, and that it acted (obviously) over the same time period, I deduced that the momentum imparted to both was equal. However, momentum is also mass times velocity. Using that knowledge, with my previously derived equations, I could further simply and eliminate my velocities, netting me, eventually, the distance of each mass to the barycenter (equivalent to the mass of the object times the radius between objects, divided by the sum of the masses).

    While you may not think this is too exciting, I found that deriving this, and then finding out I was actually right was interesting. All of these equations that were used were simple, but when applied together in the correct situation, they have the ability to solve more complex problems.
  2. oxy126
    A lot of games let you fly planes, but when was the last time one let you fly a rocket? While if that has been what you've been looking for in your time-wasting pursuits, wait no longer, for Kerbal Space Program lets you do just that. As the director/god of the aptly named Kerbal Space Program, you have the ability to launch probes, satellites, landers, space planes, and a whole plethora of fancy little stuff. But behind all of this glamour comes (simplified) rocket science. Much like real rocket scientists, you have to design a craft with fuel and power constraints in mind. Going to the Mun may not be as trivial a task as some may hope.

    If you prefer fast paced action, this game probably isn't for you. But if you're willing to think a bit, ponder questions about choosing an engine with a larger thrust to weight ratio versus one with a higher specific impulse, or how you should stage your creation to successfully land on Minmus and return home safely, this might just be your cup of tea. I recommend checking it out.
  3. oxy126
    I'm here today to discuss the possibility and implications of time travel...




    ...Just kidding. Time travel isn't real, kids, and you'll just have to get over that. But there is one thing which I think you'll find equally fascinating: PLUMBING.

    Plumbing is pretty insane. Water flowing through pipes and stuff, the transportation of liquids, at times I've found it too much to handle. As many physics students have already learned, Bernoulli's equation and stuff. It all applies to plumbing, and making sure everything flows right.

    Bernoulli's equation is important for things like constricted pipes or transporting water to the tops of tall buildings. For example, when your hose gets kinked, the water through that kink must flow faster in order to maintain the same flow rate, which requires more energy. Using Bernoulli's equation, we can see that this means the flow rate must diminish in order for energy to be conserved, causing the water in your tubing or hose to slow down, which can be a problem especially with a low-pressure water supply. On an entirely different semi-aquatic semi-plumbing topic, the venturi effect, or the effect of a fast moving stream to create low pressure areas, is used in aquariums to bring air into the marine environment while only using a water circulator to do so.

    So yeah. Plumbing.
  4. oxy126
    While it may not be necessarily very physics related, it is an interesting point on the topic of networks, both social and otherwise: the average facebook user is only 4.74 "connections" away from any other average facebook user. The article https://www.facebook.com/notes/facebook-data-team/anatomy-of-facebook/10150388519243859, while from 2011, illustrates the concept that, when the correct pathways are taken, we can all be very closely related. Building on Stanley Milgram's famous experiment trying to assess the validity of "six degrees" of separation between anybody else, this facebook analysis shows how the exponential nature of going from friends to friends of friends puts us all in a strangely close social proximity to one another. In my opinion, it is fairly astounding stuff.

    Networks, internet related or otherwise, are essentially complex structures built from basic components. Whether it is a vast array of *almost* symmetrical distributions of elementary particles giving way over the years to for stars, nebulae, planets, and even life, or just the movement and flow of a bunch of water molecules through your faucet, they are simple yet complicated, where even, as the social network experiment shows, the tiniest part of the system can have an influence on another part completely separate, influences which happen frequently and, as a result, make the prediction of these systems very difficult. Our whole physical world, everything we learn, is based on combinations of the same few elementary particles responding to elementary forces, and things like centripetal force and the laws of thermodynamics are just (often slightly simplified) mathematical models to explain the ways all of these forces and particles interact with each other. So while you can blame the weatherman for getting the forecast wrong, or just wonder why no physics engine to date has implemented a fast yet accurate fluid modelling system, just remember that the world can be a very complex, interconnected place.
  5. oxy126

    Yo Dawg, Bicycles

    By oxy126,

    Why do bicycles stay " up"? Physics, that's why. Bicycles rely on the concepts of angular momentum and precession to prevent tipping over when. When a wheel is spinning fast, it tends to resist changes in it's angular momentum. This is called 'precession', and is an important concept in bicycles and unicycles alike. When gravity tries to tilt a wheel, it is effectively trying to alter the angular momentum of the wheel. In reaction, the wheel will turn only slightly, and gain a slight 'wobble' as one side of the wheel juts out above the rest, which is usually resolved by dampening forces 'n' stuff. So bikes work because of physics, and that's pretty cray.

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