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bazinga818

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Blog Entries posted by bazinga818

  1. bazinga818
    Yay for more circular motion! So does anyone know what I'm talking about when I say "playground spinny things"? There like mini merry go rounds for playgrounds, but like...without the animals and cheesy music. Someone goes on them and you spin them really fast? There are funny fail videos on the internet of people spinning super fast on them and then flying off? Sound familiar?

    I hope so, because I really don't know what they're called. But anyway, I thought I'd talk about the physics behind them for a bit.

    So when you spin on these spinny things, you feel a centripetal force (Fc) and centripetal acceleration (ac) point towards the center of the circle. The centripetal force, Fc, is equal to mv2/r, and remembering Newton's 2nd Law (F=ma), we can then deduce that ac = v2/r.

    If, like the people in those fail videos, you were to spin so fast that you flew off the spinny things - you would fly off in a path tangent to the circle. This is because your velocity acts tangently to the circle.

    There's something I don't quite get about this, though. When you spin, you feel like you're being pulled outward away from the center of the circle...if Fc is pointed toward the center of the circle, why do you feel a force outward instead? Maybe I'm just thinking about it wrong, but either way it'd be great if someone could explain that to me.

    Thanks for reading! I hope you enjoyed a snippet of the physics behind those playground spinny things I still don't know the name of.

    Until next time,
    bazinga818

    EDIT: I guess they're actually called merry-go-rounds too? Weird. Anyway, I found a nice fail-compilation video for you to enjoy below. For some reason people seem to think it's a super awesome and profoundly intelligent idea to take a motorcycle wheel to these things...makes for a good video anyway! Yay circular motion!



    My favorite is probably the one at 1:23...that kid just goes downnnn, man. Like come on it wasn't even going that fast. What a pansy.
    And I really realllllly want to try the one at 1:51, minus the faceplant part.
    I also thoroughly enjoy the duck one.
  2. bazinga818
    So I figured it was time I do a sports post, since it seems to be a super popular blog topic recently and I can't think of anything else to do at the moment. Time for the physics of volleyball!

    Jumping right into it (haha volleyball puns ), I'll start off with the serving part. So when you serve the ball over the net, it becomes a projectile whose distance is dictated by the force at which you hit it. Assuming there is no initial vertical velocity and you hit the ball straight over the net, you can find the initial velocity by timing how long it takes for the ball to hit the ground (though that shouldn't happen in an actual game...) and measuring the distance it traveled.

    You could use the kinematics equation x = Vot + .5at^2 to find the initial horizontal velocity, which would also be the final horizontal velocity since a = 0. Then you could use the equation Vf = Vo + at to find the final vertical velocity for the ball, as you know the acceleration due to gravity is -9.8m/s and the initial vertical velocity is 0.

    Another physics-related concept in volleyball involves diving for the ball. When you dive to the side or forward for a dig, you exert a force down on the ground at an angle to push you in that direction. Since volleyball is a fast-paced sport and involves split-second decisions and actions, you would have less than a second to recognize where the ball was going and exert this force. But the force would have to be large enough to propel you to the ball; so you would exert a force of great magnitude over a very small amount of time. This would be your impulse: average force times time, or Ft.

    So those are just a few of the physics concepts related to volleyball! Hope you enjoyed!

    Until next time,
    bazinga818
  3. bazinga818
    Recently I sat at the table eating dinner, when I noticed a flutter in my peripheral vision, drawing my attention. I turned my head to see my cat batting at a cat toy someone had hung from the table...one of those sticks with the string attached and a feather or fluffy thing at the end, ya know? You wave it around like a wand and your cat pounces after it?

    Anyway, someone in my family had set it up so just the string and attached feather hung down over the table, just within my cat's reach. She batted at it playfully.

    It was then that I realized...hey! More real-life physics applications! This cat toy was an example of a pendulum!

    When we learned about pendulums, we learned that they have a period of oscillation, or time it takes for them to complete one cycle, to swing forward and back to its original position. We learned that pendulum's periods of oscillation DO NOT depend on the mass of the object at the end of the pendulum (as with springs), but rather only depend on the length of the pendulum and the acceleration due to gravity.

    For a perfect pendulum (weightless string, perfect conditions, etc), the equation for the period is T = 2(pi)radical(L/g), or 2 pi times the square root of length of the pendulum over acceleration due to gravity.

    Unfortunately, my cat's toy wasn't a perfect pendulum, and the feather at the end inhibited the period time due to the air resistance it created...but oh well, she didn't seem to mind.

    Thanks for reading!

    Until next time,

    bazinga818
  4. bazinga818
    As much as I'd like to tell you I've figured out all the physics of being invisible and how to acquire it as a superpower, I would be lying. To add insult to injury, this post isn't even about the physics of invisibility, but rather about why true invisibility is an impossibility due to the laws of physics. So if you don't want all your dreams of becoming a superhero with powers of invisibility to be crushed, it would be advisible to stop reading here! To everyone sticking around, be prepared to have your mind blown.

    To be truly invisible is to have light pass through you. You are still a solid being, but no one can see you because light passes through you rather than reflecting off of you. So as not to freak passersby out, it's assumed you would have to be naked pretty much all the time, and never carry anything on you - otherwise people would see floating clothes and objects.

    Naked outside in the middle of winter? And if it rains, the drops would bounce off of you, making your outline visible. This would happen eventually just with dust particles that collect on your skin too. Not to mention constantly having to dodge people and making sure you don't get run over by cars. Sounds fun so far.

    So, now on the physics mind-blowing part. What do you think the world would look like if you were invisible? The answer? Nothing. You see things because light bounces off of them and reflects in your eyes, right? That's why we can't see in the dark; there's no light. Well, if you were invisible, by definition light would pass through you - so images couldn't be reflected in your retinas for your brain to interpret and turn right-side up.

    I deeply apologize if I have ruined any of your fantasies, reader. But, if invisibility were a possibility, you wouldn't be able to see anything or anyone any more than they could see you. You would be blind. Trust me - I wasn't happy about it either.

    To those of you who are impartial to the subject of superpowers, I hope you enjoyed this blog post! Thanks for reading, and until next time:
  5. bazinga818
    Recently (on a much cooler day), I discovered something while driving to volleyball practice at night. It was chilly so I had the heat on in my car, but just on low. Upon turning on the highway, I suddenly noticed that the heat seemed to have been turned up! That wasn't right, how could it do that on its own?! I double checked it, but the switch hadn't moved; the heat was still on the lowest setting.

    So why did it feel like hot air was blowing twice as fast into my face? Well, when I thought about it, the answer was simple: inertia. As the car accelerates forward (as it does when entering a highway), the objects - including hot air - inside the car want to stay put. This is the same reason why you feel thrust forward when you slam on the breaks, or slammed against the wall when you make a sharp turn. Your body wants to keep moving in a straight line due to inertia (as Newton says, "an object in motion tends to stay in motion").

    So, what does this have to do with the hot air in my car? Well, it too has inertia and wants to stay at rest unless acted upon by an outside force, so when I accelerated onto the highway, the hot air stayed in place. Since the car itself was accelerating forward while the air stayed put, it made it feel like the hot air setting had been turned up as it blasted in my face. In reality, it was me (and the car) accelerating into the hot air.

    Anyway, I thought this was pretty cool. Hopefully you thought so too! Thanks for reading.

    Until next time,

    bazinga818

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