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A puck slides a total of 12m: Problem relating kinteic friction to Newton's law

  1. Nov 1, 2009 #1
    1. The problem statement, all variables and given/known data

    In a shuffleboard game, the puck slides a total of 12 m before coming to rest. If the coefficient of kinetic friction between the puck and board is 0.28, what was the initial speed of the puck?

    2. Relevant equations
    f=ma
    fk=U*N
    vf^2=v^2+2ad
    a=delta v/t


    3. The attempt at a solution

    I tried to find the acceleration using the equation above but since I don't know the initial speed, I get 2 unknown. I tried to substitute a by delat v/t but I don't have time either. I don't have the mass of the puck either so I can't find the normal force. How can I start?
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. Nov 1, 2009 #2

    Doc Al

    User Avatar

    Staff: Mentor

    Use Newton's 2nd law to find the acceleration. (You don't need the actual mass--just call it m.)
     
  4. Nov 1, 2009 #3
    From Newton's law: you can find accleration of puck.
    P + Ff + N = ma

    After find a, you will use this eq:
    [tex]v^2 - v_0^2= 2as[/tex]

    Because puck is at rest after going distance = 12m, v = 0. Plug a, then you get answer.
     
  5. Nov 1, 2009 #4
    Thanks to both of you, I got it! I didn't see the masses canceled in the first equation.
     
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