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Finding coeffiecient of friction

  1. Feb 10, 2015 #1
    1. The problem statement, all variables and given/known data
    You give a 2.85kg book an initial shove at 2.98m/s and it comes to rest after sliding 3.80m across the floor.
    Find the coefficient of friction between book and floor.

    2. Relevant equations
    vf^2=vo^2+ad
    f=ma
    3. The attempt at a solution
    0=2.98+a*3.8
    =2.33
     
  2. jcsd
  3. Feb 10, 2015 #2

    gneill

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    Staff: Mentor

    I think you'll need to explain your attempt. What were you trying to accomplish?
     
  4. Feb 10, 2015 #3
    i tried solving for a in order to use f=ma
     
  5. Feb 10, 2015 #4

    gneill

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    First, verify that your relevant equation is written correctly and not missing any constants.

    Next, I don't see where in your attempt you accounted for squaring the initial speed. You don't seem to have applied the relevant equation.
     
  6. Feb 11, 2015 #5
     
  7. Feb 11, 2015 #6
    I did with conservation of energy. By equating kinetic energy to the frictional work done,

    1/2*mv^2=(mu)*N*d

    Where m is mass
    v is initial velocity
    mu is coefficient of friction
    N is normal force i.e. mg
    d is distance travelled

    I got an answer, mu = 0.16
     
  8. Feb 11, 2015 #7

    Svein

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    Going another route, I arrived at the same expression. But - I seem to have a slightly different answer: μ≈0.12.
     
  9. Feb 11, 2015 #8
    That could be possible because of certain approximations in the calculation, like value of "g", or something else, i guess.
     
  10. Feb 11, 2015 #9

    haruspex

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    No, 0.16 looks too inaccurate for that. Note that the mass is irrelevant.
    But more seriously, you are not supposed to present something so much more Like a complete solution than the original poster has yet managed. Gneill's post is the right sort of hint.
     
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