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Conservation of energy of a toboggan problem

  1. Mar 27, 2009 #1
    1. The problem statement, all variables and given/known data
    A loaded 305kg toboggan is traveling on smooth horizontal snow at 4.60m/s when it suddenly comes to a rough region. The region is 9.00m long and reduces the toboggan's speed by 1.10m/s.


    2. Relevant equations

    What average friction force did the rough region exert on the toboggan?

    3. The attempt at a solution

    I know you can find the initial conditions of the kinetic energy and then the final conditions given the final velocity. I just don't know how to get the force of the rough region. Any help is appreciated.
     
  2. jcsd
  3. Mar 27, 2009 #2

    djeitnstine

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    How much average deceleration of the toboggan was there? You have the initial v, final v and the distance it decelerated by.
     
  4. Mar 27, 2009 #3
    -.12m/s
     
  5. Mar 27, 2009 #4

    djeitnstine

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    Is that negative velocity? Check your units. Also in the case that is acceleration, then where is the problem of finding the average force of friction? [tex]\bar F_f=m \bar a[/tex] where a is the average deceleration experienced.
     
  6. Mar 27, 2009 #5
    It would be simple but am I correct in saying the average acceleration (deceleration in this case) is -.12m/s^2? Because when I do -.12*305 it is not correct. The friction force would be -37.3N which is incorrect.
     
  7. Mar 27, 2009 #6

    djeitnstine

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    The correct formula to find acceleration with a distance, and 2 velocities is [tex]v^2_f=v^2_i+2ax[/tex] x=distance, a=acceleration
     
  8. Mar 27, 2009 #7
    Ah of course. I knew that. Thanks!
     
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