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Finding Distance using friction Urgent Help Please

  1. Mar 7, 2007 #1
    1. The problem statement, all variables and given/known data
    There is an object that is 10kg. This objects initial speed is 10 m/s. The friction working against the object is .1---What is the distance to when the object stops moving?

    2. Relevant equations


    3. The attempt at a solution

    u(k)= f(k)/N...The N, i think, is 100 because of the gravity (10) and the weight of the object (10). Then i had to multiply that by the U(k), (.1), which gave me 10. Then i used f=ma. The mass is 10 kg and the force is 10, which gave me the acceleration of 100 m/s, which does not make sense.

    I did not know where to go from there.
     
  2. jcsd
  3. Mar 7, 2007 #2

    Doc Al

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    Staff: Mentor

    Why did you multiply mass times force to get acceleration? (Rewrite "F=ma" to solve for the acceleration.)
     
  4. Mar 7, 2007 #3
    Ok...But that will only give me 1 m/s. How would I then solve to find how far the object will go until it stops.
    thanks
     
  5. Mar 7, 2007 #4

    Doc Al

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    Since you've gone to the trouble of finding acceleration, you may as well use it. What kinematic formula relates distance to speed and acceleration?

    If you've covered energy methods, you can also calculate the work done by friction to bring the object to rest. Same answer, of course, but it might be easier.

    (Also: The unit for acceleration is m/s^2, not m/s--that's velocity.)
     
  6. Mar 7, 2007 #5
    Maybe d=st...but I only know speed.
     
  7. Mar 7, 2007 #6

    Doc Al

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  8. Mar 7, 2007 #7
    [tex]x = x_0 + v_0 t + (1/2) a t^2[/tex]
     
  9. Mar 7, 2007 #8
    will that work?
     
  10. Mar 7, 2007 #9

    Doc Al

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    Since you don't have the time, if you use that formula you'll need to use another one to find the time.

    But there's another formula that has exactly what you need with no extra variables. That will allow you to solve for distance in one step. Find it.
     
  11. Mar 7, 2007 #10
    Velocity - initial velocity / acceleration = time....So the velocity would be 1 - 10 divided by 10...Am I right? which would give you .9....???
     
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