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Homework Help: Balance the force to find the angle

  1. Sep 13, 2010 #1
    1. The problem statement, all variables and given/known data

    A mass, m = 175 gram is placed on a hanger which has a mass of 50 g, giving a total mass of 225 g. The hanger is then hung at an angle of 120° over a pulley attached to the force table by using a string of negligible mass. The pulley over which the string rests has very low frictional force.
    34fb6vm.gif
    110egs7.png

    In order to balance the force F another mass needs to be hung from the force table. What is the total mass (mass plus hanger) needed to balance the force F? At what angle should the mass be hung? Give your angle from the positive x-axis.

    2. Relevant equations
    Tx=Tcos(theta)
    Ty=Tsin(theta)
    A=SQRT(X^2+Y^2)
    T= mg

    3. The attempt at a solution
    T = 2.2 N from .225*9.8
    Tx=2.2cos120=-1.10N
    Ty=2.2cos120=1.91N

    Mass to balance = 225g
    Angle = -30degrees?

    the way I was told to find the angle was to draw the negative of the angle, so I drew the vector on the opposite side of the 2nd quadrant onto the 4th quadrant. Then find the angle according to the +x-axis. I drew the angle and for me I got -30 degrees since I assumed that since the 1st quadrant is 90degrees, then the remaining degree on the 2nd quadrant is obviously 30 and the opposite of it into the 4th quadrant would be -30?


    Any hints/help would be appreciated. Thanks



    edit :Wow - nevermind... I figured this out lol. Ignoring this problem and coming back to it an hour later works wonders :P
     
    Last edited: Sep 13, 2010
  2. jcsd
  3. Jan 22, 2011 #2
    Hey....how'd you figure it out? I'm stuck at the same place and with your previous answers lol. Any help would be appreciated
     
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