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Homework Help: Force Applications

  1. Feb 8, 2006 #1
    Can anyone help me to solve for the distance here ?? i'm lost ...

    A baseball player slides with an initial speed of 7.9 m/s. If the coefficient of kinetic friction between the player and the ground is 0.41, how far does thet player have to slide before comming to rest ?
  2. jcsd
  3. Feb 8, 2006 #2


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    Can you calculate the magnitude of the deceleration (Hint: make a free body diagram and use Newton's second law; the mass of the player will cancel out)?

    (You can also use the work-energy theorem if you have covered that in class.)
  4. Feb 8, 2006 #3

    can anyone expand on this explanation ? im still lost
  5. Feb 8, 2006 #4
    u could calculate force that will decelerate the baseball player using the coefficient of kinetic friciton

    [tex] \mu_k = \frac{F_{fr}}{F_{N}} [/tex]

    figure out the deceleration from that force...

    then use a kinematic equation to solve for distance

    [tex]{v_0^2} = {v_1^2} + 2ax[/tex]
    Last edited: Feb 8, 2006
  6. Feb 9, 2006 #5


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    The only force acting on the player is friction, so Newton's second law gives:

    [tex]F_{net} = ma = f = -\mu mg [/tex]

    The mass cancels out when you solve for a:

    [tex] a = -\mu g [/tex]

    Now that you have the magnitude of the acceleration, you can use the kinematic equation suggested by teken894, which should be written:

    [tex] v^2 = v_o^2 + 2a\Delta x [/tex]
    Last edited: Feb 9, 2006
  7. Feb 9, 2006 #6


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    Nope, it shouldn't be written like that. It should instead read:
    [tex]v ^ 2 = v_0 ^ 2 + 2ad[/tex]
    Note that it's v2 not v. :)
  8. Feb 9, 2006 #7


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    Oops. Sorry about the typo. Fixed now.
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