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Partice Kinetics Question - HELP

  1. May 11, 2009 #1
    1. The problem statement, all variables and given/known data
    As shown in the attachment.
    At the instant shown the block is moving down the slope. What is the acceleration of the block up the slope if the kinetic coefficient of friction is 0.4?


    3. The attempt at a solution

    I'm having problems with two things here, the calculation of the normal reaction on the block as i dont know what to do about the angle of the line on the pulley and its resultant force...
    This leads to my second problem when summing the total force in the x-direction i still dont know what to do with the 47N force....

    Generally i need help!
     

    Attached Files:

  2. jcsd
  3. May 11, 2009 #2

    tiny-tim

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    Welcome to PF!

    Hi Cam169677! Welcome to PF! :smile:

    (is 31º the angle between the upper rope and the slope, and is the lower rope suppposed to be parallel to the slope? :confused:)
    There's no acceleration in the normal direction, so just use good ol' Newton's second law in that direction … ∑F = 0. :wink:
    what's the x-direction?

    the obvious direction to use is the direction of the slope …

    then the component of the 47N in that direction is 47(cos31º)N
     
  4. May 13, 2010 #3
    I'm also having trouble with this.

    "is 31º the angle between the upper rope and the slope, and is the lower rope suppposed to be parallel to the slope?"

    That's what i want to find out as well hmm
     
  5. May 13, 2010 #4

    tiny-tim

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    Welcome to PF!

    Hi PcKSnipE! Welcome to PF! :smile:
    I assume it is.
     
  6. May 15, 2010 #5
    Alright i worked it out, the tricky bit has to do with the pulley.

    The total force of the pullet in the X plane is T + TcosA
    The force in the normal direction (which affects friction) is mgcosA - TsinA

    Gl
     
  7. May 9, 2011 #6
    i still dont get wat to do here guys i have a similar question but using the following example can u tell me step by step wat to do and a answer as well
    Thanx much appreciated
     
  8. May 9, 2011 #7

    tiny-tim

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    welcome to pf!

    hi jalwa! welcome to pf! :wink:

    better start a new thread …

    make sure to show us what you've tried, and where you're stuck, and then we'll know how to help! :smile:
     
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