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Does anyone else find themselves making up strange formuale?

  1. Nov 16, 2007 #1

    rock.freak667

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    I mean like one day...I some how proved that a girl's attraction to a guy is directly proportional to the amt. of money he has and proportional to how much game he has...btw these things arent taken seriously
     
  2. jcsd
  3. Nov 16, 2007 #2

    Mk

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    Yeah. Usually mine start out as "hmmm, x could be described as a function of z and y over time—"
     
  4. Nov 16, 2007 #3

    mgb_phys

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    Or the mass of an SUV is inversely proportional to the mass of the sole child in the back.

    The ability of a car to stop at an amber light is inversley proportional to the price of the car ( except for car=BMW -> ability=0 )
     
  5. Nov 17, 2007 #4

    BobG

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    Yes. Like what exactly are the chances that the bread lands butter side down?

    You have about four or five main problems to figure out.

    1) As you slowly push the bread, eventually it's center of mass will be beyond the table edge and you'll have a small amount of torque, causing the bread to begin rotating. You could continue pushing the bread or stop pushing the bread:

    a) If you continue pushing the bread, the center of mass is moving further past the table edge and the amount of torque is increasing, increasing the angular acceleration, increasing the rate the bread is rotating, but you're also decreasing the time that torque will be applied.

    b) You could stop pushing the bread, giving you a constant torque and a constant angular acceleration. The main difference from a is that you have a slower angular velocity once:

    2) You reach some angle an which the bread will overcome its coefficient of friction and begin sliding off of the table, moving the center of mass and increasing your torque. Additionally, you now have some downward translational motion. Because you have both rotational and translational acceleration, the translational acceleration is less than the gravitational acceleration constant.

    3) Eventually the far end of the bread has moved past the table and you have no more angular acceleration. The bread will now rotate at a constant angular velocity (whatever that may be). You should be able to get at least a rough estimate based on the length and thickness of the bread. The bread will accelerate at 9.8 meters/second^2. If you know fast the bread is rotating, it should be easy to figure out how the bread will land based on how long it will take for the bread to reach the floor.

    4) Three's not really true because of air resistance. The bread has a large cross-sectional area to mass ratio when it's paralel to the ground. It has a small cross-sectional area when it's perpendicular to the ground. That means you really have a varying angular velocity and a varying translational acceleration all the way the down to the floor.

    5) I can virtually guarantee you the bread won't have time to rotate 180 degrees unless you have small bread, a tall table, or the bread was dropped onto the table edge giving you a large amount of torque right off the bat. It will almost certainly rotate past 90 degrees unless you have extremely large bread, a very short table, or the bread spent a very small time on the edge of the table (the only place angular acceleration can be positive). Hitting at an angle creates a whole new problem since the edge of the bread will bounce. Figuring out a good equation to evaluate the bounce is a lot tougher than figuring an equation for the bread's rotation. I think it would almost be easier to do a lot of experimenting and then create an equation that roughly matches the results of the experimentation. You can make some generalizations about what to expect though. The more the impact is cushioned, the less dramatic the bounce will be. The closer to 180 degrees the rotation is, the better the chances the bread will settle butter side down (instead of rotating past 270 degrees on the bounce).
     
  6. Nov 17, 2007 #5
    This has been attributed to Einstein, but I doubt it:

    Let X = work, then Happiness = X + Y + Z where Y = play, and Z = mind your own business.
     
  7. Nov 17, 2007 #6

    BobG

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    (Grace + Efficiency) * Style = Satisfaction

    I'm not sure I like that equation, though.

    I kind of disagree with so much emphasis on style (unless you're talking about jeans).

    The balance between grace and efficiency might be approximately right, though. Brute force might sometimes be the most efficient, but, being kind of a skinny guy, I tend to prefer more finesse.

    In fact, one of the toughest things I ever had to do was teach my youngest son, whose built like a tank, how to change a tire. The whole reason for a four-way is that you don't have to brute force the lug nuts off. And it would it really be that hard to actually move your body a little so you actually had a better angle? I swear, if he ever gets a flat tire, he's going to have to flag down a little old lady to get the lug nuts off for him.
     
  8. Nov 17, 2007 #7
    time * money = girls
     
  9. Nov 17, 2007 #8

    robphy

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    Gold Member

  10. Nov 17, 2007 #9

    matthyaouw

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    Do I think up formulae!? No! My interests lie in geology. I much prefer to pick out textures and structures present in the local architecture...

    ...

    I'll get my coat...

    /leaves
     
  11. Nov 17, 2007 #10

    BobG

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    That reminds me of a song:

    If you got the money, honey....
     
  12. Nov 17, 2007 #11
    I've Got The Ti-ime
    We'll go honky-tonkin'
    And we're gonna have a time
     
  13. Nov 17, 2007 #12

    Mk

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    We've got your disease!
    Jungle!
    Welcome to the Jungle!
    Shu na na na na na knees! kneees!
     
  14. Nov 17, 2007 #13

    rock.freak667

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    haha...welcome to the jungle..a classic..

    To BobG: That was a funny post about the bread landing butter side down
     
  15. Nov 18, 2007 #14
    The newness of a area rug directly correlates to the amount of vomit a cat can produce.
     
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