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High School Question about Friction

  1. May 25, 2004 #1

    JasonRox

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    If the coeficient of friction is 0, than I don't need any force to push it?

    If it is .5, I only need to push 50% of it's total vertical force?

    I think I got this right.

    Which is why sliding is sometimes more efficient than lifting, right?

    If something had a coeficient of 1.5, you are better off lifting it off the ground.
     
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  3. May 25, 2004 #2

    Alkatran

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    The friction coefficient is not the percent of force which is resisted, it's the ratio between the force between object/ground and friction.

    For example, you know that gravity accelerates everything downwards at 9.8 m/s^2 so if we had a 5 Kg block sitting ona surface with a coefficient of 2:

    Friction = Fn * u
    Fn = -Fg
    Fg = -9.8*m
    Friction = -Fg * u = --9.8*m*u = 9.8*5*2 = 98 Newtons

    So if you push the block, you need to push with more than 98 newtons to accelerate it.
     
  4. May 25, 2004 #3

    HallsofIvy

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    "The friction coefficient is not the percent of force which is resisted, it's the ratio between the force between object/ground and friction."

    But that's what Jason Rox said: " 50% of it's total vertical force?"

    Essentially, yes, in order to keep something moving at a constant speed on a horizontal surface, you must apply a force equal to the friction force which is the friction coefficient times the "total vertical force".
     
  5. May 25, 2004 #4

    Gokul43201

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    I doubt you'll ever come across a pair of surfaces with mu = 1.5.
     
  6. May 31, 2004 #5

    JasonRox

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    It's been awhile, but in the end, because frictional force rarely goes above it's vertical force, everyone chooses to slide big objects.
     
  7. May 31, 2004 #6
  8. May 31, 2004 #7

    JasonRox

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    It is possible, but it is unlikely.

    Friction exists because surfaces are uneven if you look REALLY close. You see little bumps, which the object must overcome to slide across the surface.

    So if the surface consisted of walls, like a maze, it would be quite difficult to slip a television through without going around the walls. In the end, the bigger the bumps, chances are the coeficient of friction is higher.
     
  9. May 31, 2004 #8
    Try putting two pieces of glass on each other...

    cookiemonster
     
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