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Homework Help: Finding the speed of a block moving on an incline

  1. Sep 29, 2011 #1
    I apologize i do not have a picture to show.

    1. The problem statement, all variables and given/known data[/b]
    A block of mass 250g is at rest on an incline that makes an angle of 30 degrees to the horizontal. The coefficient of kinetic friction between the block and the plane is 0.10. The block is attached to a second block with a mass of 200 g that is connected by a light string that passes over a mass-less, frictionless pulley. When the hanging mass has fallen 30 cm, what is its speed?

    2. Relevant equations[/b]
    Fk = μkN
    sum of the Forces = ma
    N-Weight(perpendicular to incline)=0 where N is the normal force (for block on incline)
    T-W=0 Where T is = tension and W = weight of the hanging mass

    3. The attempt at a solution[/b]
    Unfortunately i do not understand how to set up this problem and solve for the speed. I know that the blocks are first at rest is first at rest so the sum of the forces acting in parallel to the incline are 0. I know that the movement of the hanging block is equal to the movement of the block on the incline. But from there i am stuck. In my book it just gives an answer .84 m/s but it doesnt show me how to get that answer. Any tips on how to approach this kind of problem would be very appreciated <3
  2. jcsd
  3. Sep 30, 2011 #2


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    Staff: Mentor

    Step 1. Draw a large diagram on which you can mark what you are given, and what you can calculate.

    Step 2. Determine the forces (due to weight) that act on the blocks in the direction that the blocks are moving.
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