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Non-consecutive forces with block and string

  1. May 13, 2014 #1
    1. The problem statement, all variables and given/known data
    a 4-kg block is attached to a string 2 m in length rotates on a horizontal surface. (a) If the co-efficient of friction between the block and the surface is .25, find the work done by the force of friction in each revolution of the block.

    2. Relevant equations
    Wnc= (KEf-KEi)+ (PEf-PEi)

    3. The attempt at a solution
    I attempted to find the work done by friction by multiplying the co-efficient of friction by the weight of the object and then multiplying that by the total distance around the circle. Unfortunately I couldn't find the distance around the circle based on the information provided. The answer to this problem was -123 J
  2. jcsd
  3. May 13, 2014 #2
    Is the block tied to a string that is pinned to the circle's center?
  4. May 14, 2014 #3
    I'm not sure
  5. May 14, 2014 #4
    It works that way so I get it now. Thanks!
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