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Pulling an object with a rope

  1. Sep 22, 2009 #1
    1. The problem statement, all variables and given/known data

    1) What is the net force on the block? (Cartesian Coordinate system)
    2) What is the X component of the tension force on the block
    3) What is the x-component of the force exerted by the floor on the block (the friction force)?
    4) What is the y-component of the force exerted by the rope on the block?
    5) What is the y-component of the force exerted by the Earth on the block?
    6) What is the y-component of the force exerted by the floor on the block (sometimes called the "normal" force, because it is perpendicular to the floor)?

    I pull on the rope with the force of 290 N
    Mass of block is 22kg
    Block moves at constant 1.3m/s
    Angle of 35 degrees with the floor.


    2. Relevant equations
    p=mv
    [tex]\Delta[/tex]p=fnet[tex]\Delta[/tex]t
    ma = T - W
    Ff = [tex]\mu[/tex]N

    3. The attempt at a solution
    1) The net force will be the total force acting on the block, therefore in the X direction it would include the X component of the force I exert, and the Y component of the force I exert minus the force of gravity acting on the object.
    Fx, me = 290 N * cos(35) = 237.55
    Fy, me = 290 N * sin(35) = 166.34
    Fgravity = mg = 215.6
    Therefore <237.55, (166.34-215.6), 0>

    2) Velocity is constant, so no acceleration, therefore T = W. Therefore, I dont know where to go with this.

    3) I do not know mu, dont know how to solve for the force of friction.

    4) Would this be equal to the force I exert on the rope multiplied by the sin of 35?
    290sin(35) = 166.34

    5) Already calculated this as well, Fg = mg = 215.6

    6) Equal and opposite of Fg?
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
    Last edited: Sep 22, 2009
  2. jcsd
  3. Sep 22, 2009 #2

    kuruman

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    Homework Helper
    Gold Member

    For question 1
    What is the acceleration of the block?
    How is the acceleration of the block related to the net force acting on it?

    Once you get the answer to question 1 sorted out the rest should be easier to handle.

    Clarification
    Your problem statement does not give the mass of the block. What is it?
     
  4. Sep 22, 2009 #3
    For question 1) Thanks! Of course, the net force is going to be 0 if there is no acceleration.

    For mass of object, had a typo, what was originally mass of rope should be mass of block (22kg) the mass of rope/myself is supposed to be negligible, i apologize.

    Figured out 2.

    For 3, how do I calculate Ff without knowing [tex]\mu[/tex]?

    Figured out 4 & 5

    For 6, is it the sum of earth + rope forces, multiplied by 1 (since its opposite direction)?
     
  5. Sep 22, 2009 #4

    kuruman

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    The sum of the horizontal components of the net force must be zero. Just balance the forces. "To the right" is positive, "to the left" is negative.

    Figured out 4 & 5

    The sum of the vertical components of the net force must be zero. "Up" is positive, "down" is negative.
     
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