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Help understanding a problem

  1. Sep 4, 2009 #1
    Ok so I have this problem and it seems pretty simple but Im not getting what its trying to say.

    According to Car and Driver, an Alfa Romeo going 70 mph requires 177 feet to stop. Assuming that the stopping distance is proportional to the square of the velocity, find the stopping distance required by an Alfa Romeo going at 35 mph and at 125 mph.

    How do you set this up, do I have to find an equation of a parabola whith the point (70, 177) and then find the others using it? The way its worded im not sure can any one confirm this or clerify it better for me?
  2. jcsd
  3. Sep 4, 2009 #2


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    If two quantities are proportional to one other, then their quotient is a constant.
  4. Sep 4, 2009 #3
    Thank you, I got it right.
  5. Sep 4, 2009 #4
    Ok what about this one,

    Poiseuille's Law gives the rate of flow, R, of a gas through a cylindrical pipe in terms of the radius of the pipe, r, for a fixed drop in pressure between the two ends of the pipe.

    If R = 430 cm3/s in a pipe of radius 2 cm for a certain gas, find a formula for the rate of flow of that gas through a pipe of radius r cm.
  6. Sep 4, 2009 #5


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