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Homework Help: Static friction force? mew? do what now?

  1. Dec 8, 2004 #1
    :( static friction force? mew? do what now??

    Okay, thanks for helping me first off.
    Second, i was absent :( and now I'm pretty confused on a few problems that do with force.
    the first of four problems, i dont understand, like, what exactly is mew?
    ok ..
    1. a 225 kg crate is pushed horizontally with a force of 710 N. If the coefficient of friction is .20, calculate the acceleration of the crate.
    Heres what ive done:
    225 kg= F sub g
    710 N= F sub p
    a = ?
    now is the coefficient of friction static or kinetic? does it matter?
  2. jcsd
  3. Dec 8, 2004 #2
    Coefficient of friction is mew. Do you have the formula for coefficient of friction, the one with Ff in it? I can't recall the meaning of what coefficient of friction is but if you have your formula for it you should be able to find acceleration.
  4. Dec 8, 2004 #3
    well, we have this formula..but its really confusing to me.
    KINETIC FRICTION FORCE: Ff, kinetic=mewk times Force normal

    ???????????????????????????????????????????????? whoa thats got no acceleration. im confused and frustrated :(
  5. Dec 8, 2004 #4
    nevermind ill take a zero lol it doesnt matter.
  6. Dec 8, 2004 #5
    I know how to do the problem now then. I'll give you some formulas and information, you can then try and attempt it.

    Ff = Mew x Fn

    Fn = -(Weight)
    W = mg (gravity = g = -9.8 m/s^2
    Weight is always negative. Fn (normal force) is what causes something to stay in place; therefore, it is opposite but equal to weight. Fn is positive.

    Once you have Ff you know:

    Fnet (net force) = Fapp (force applied) + Ff (force of friction)
    Force of friction is negative:

    Fnet= Fapp + (Ff) - The + will combine with the - from Ff and make the problem subtraction.

    Once you have Fnet:

    Fnet = ma

    Fnet divided by mass = a

    Then you have acceleration.
  7. Dec 9, 2004 #6
    Yupp - that's right :)
  8. Dec 9, 2004 #7
    To clear understanding...mew indeed is the coefficient of friction

    it is defined as the Frictional Force (F of F) over (/) the Normal Force (F of N)

    Mew helps to understand the tendency of an object to slide..

    For instance, an object with .5 mew takes much more force to slide it horizontally than an object with a .3 mew.
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