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Finding displacement with coefficient of friction, mass and velocity

  1. Oct 13, 2011 #1
    1. The problem statement, all variables and given/known data
    A physics student slides a 2.0kg textbook along the laboratory bench to her friend. She imparts to the book an initial velocity of 2.70m/s. μ=0.20. How far away is her friend if the book comes to a stop right in front of her friend

    Vi= 2.70m/s μ=0.20 m=2.0kg Vf= 0m/s d=?
    2. Relevant equations3. The attempt at a solution
    We were taught to figure out everything we could possibly figure out, relevant or not.
    FN=Ff (no vertical movement)

    Ff=μFN
    Ff=(0.20)((2.0kg*9.81m/s2))
    Ff=20N

    Fnet(Fa-Ff)=ma then use Vf2=Vi2+2ad and solve for d? I just don't know how to find Fa or acceleration with the given variables. Is Fnet equal to Ff in the direction opposite of acceleration/Fa? Does that help?

    We haven't done anything with μ and mass combined with velocity to find distance.
     
  2. jcsd
  3. Oct 13, 2011 #2
    The only equations we have are:
    Fnet=ma Fg=mg Ff=μFN
    a=(Vf-Vi)/t
    Vf2=Vi2+2ad
    d=Vit+1/2at2
    d=[(Vf+Vi)/2]t
     
  4. Oct 14, 2011 #3

    NascentOxygen

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    Staff: Mentor

    The book would keep on sliding along at 2.7 m/sec, except there is a frictional force slowing it down. What is the acceleration (i.e., deceleration) that friction causes to the book? Once you have determined the value for a, the rest is easy.
     
  5. Oct 14, 2011 #4
    So the acceleration would be negative and friction would influence it. I just don't know what to use to find Fnet, not knowing Fa. Is Fnet -4.0N ? The negative force of friction?
     
  6. Oct 14, 2011 #5

    NascentOxygen

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    Staff: Mentor

    I don't know what you call Fa, but there is only one force acting on the book, and that's friction. The net force acting on the book is -4N.
     
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