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Due Tommorrow:Hockey Puck shot across the ice(trying to find coefficient of friction)

  1. Dec 17, 2008 #1
    1. The problem statement, all variables and given/known data

    A hockey puck is hit on a frozen lake and starts moving with a speed of 12.0m/s. Exactly 5.0sec later, its speed is 6.0m/s. What is the puck's average acceleration? What is the coefficient of kinetic friction between the puck and ice?

    2. Relevant equations
    VF=VI+at
    FN=mg
    FF=UFN
    FF=ma
    EFY=FN+Fgcos(0)
    (cos(0)=1)

    3. The attempt at a solution
    I have the acceleration it's -1.2m/s2 (that was easy been doing that for a while)The problem is I am having trouble on finding the coefficient of Friction. I'm pretty sure the last four equations are correct, do i need to find Fn next? Because i don't have the mass and it's not moving at a constant velocity, so i do need mass right?if and multiply that by gravity to get Fn? All I know i have the info just a little confused on how to use it


    Never mind i got it no worry's
     
    Last edited: Dec 17, 2008
  2. jcsd
  3. Dec 17, 2008 #2
    Re: Due Tommorrow:Hockey Puck shot across the ice(trying to find coefficient of frict

    If you solve the equation for FF=ma, you'll find that the m's cancel out.
     
  4. Dec 17, 2008 #3
    Re: Due Tommorrow:Hockey Puck shot across the ice(trying to find coefficient of frict

    uh? what do u mean m's cancel out? The mass cancels out? and ya that's one formula forgot (i edited it in)
     
  5. Dec 17, 2008 #4
    Re: Due Tommorrow:Hockey Puck shot across the ice(trying to find coefficient of frict

    Yes. You'll find that writing the frictional force in terms of m,g, and u and setting it equal to ma will result in the masses canceling out.
     
  6. Dec 17, 2008 #5
    Re: Due Tommorrow:Hockey Puck shot across the ice(trying to find coefficient of frict

    edit: yep ^^^^^^^^

    I believe he/she means that you can replace m*a for the force of friction, so:

    -1.2m = k*-9.81m

    By solving this, you see that the mass cancels and you're left with the coefficient of friction.
     
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