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Pulley system on an inclined plane with friction.

  1. Sep 26, 2013 #1
    1. The problem statement, all variables and given/known data

    Two blocks are connected by a thin inextensible string over a frictionless massless pulley
    as shown on the picture below
    The acceleration of gravity is 9.8 m/s2

    Given that the two blocks move at 1.9 m/s
    under an acceleration of 4.1 m/s2,
    calculate the coefficient µk of kinetic friction between
    the left block and the incline.

    2. Relevant equations*
    ƩF=MA
    Ffk*Fn
    m2-T = m2*a

    *(any and all derived equations as well)


    3. The attempt at a solution
    Tension minus parallel force of gravity minus force of friction equals zero because its travelling at a constant velocity.

    (110kg*(9.8m/s2-4.9m/s2)) - (37kg*9.8m/s2*sin(33)) - (μ*9.8m/s2*37kg*cos(33))

    after doing the arithmetic and algebra i got to:
    429.5138859N = (μ*9.8m/s2*37kg*cos(33))

    Dividing both sides by (9.8m/s2*37kg*cos(33))
    i got μ=1.412400969

    I got this incorrect twice before and know have noticed my previous errors and fixed them, but was wondering if anyone can verify with me that this is the right/ wrong answer? thanks!
     

    Attached Files:

  2. jcsd
  3. Sep 26, 2013 #2

    ehild

    User Avatar
    Homework Helper
    Gold Member

    The text of the problem is confusing, but the blocks do not move with constant velocity: There is acceleration of 4.1 m/s2. v=1.9 m/s at an instant.


    The equation is not correct. It should be ƩF=(m1+m2)a, the sum of all external forces is equal to the acceleration of the whole system multiplied by the mass of the whole system. What is that 4.9 m/s2?

    ehild
     
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