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Homework Help: Frictionless inclined plane problem

  1. Oct 15, 2012 #1
    1. The problem statement, all variables and given/known data

    A 2.5 kg block is placed on a movable 40° ramp weighing 120 N. The friction
    coefficients between the ramp and the block are μk = 0.15 and μs = 0.35. With what
    force does the ramp need to be pushed to keep the block

    a) sliding at a constant speed up the ramp

    b) sliding at a constant speed down the ramp

    c) what range of forces keeps the block stationary on the ramp

    2. Relevant equations

    The only equations i can think of is F=ma, Ff= μk*mg

    3. The attempt at a solution
    I tried resolving the forces into components parallel to the acceleration's direction,
    so for a general free body diagram of all the situations

    ƩFa=ma= Fgxcos(40)+Ffcos(40)


    Where signs can be changed according to actual situation

    That's where i got stuck, I actually have the solution to this problem, but i didn't understand how the answer came about. Can anybody please offer some help? If you want i can also put the solution here
    1. The problem statement, all variables and given/known data

    2. Relevant equations

    3. The attempt at a solution

    Attached Files:

    • FBD.jpg
      File size:
      11.5 KB
  2. jcsd
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