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Finding Tension of a string tied to a wall

  1. Sep 22, 2015 #1
    In the figure we see two blocks connected by a string and tied to a wall, with θ = 33°. The mass of the lower block is m = 0.9 kg; the mass of the upper block is 4.0 kg. Find the tension in the string that is tied to the wall.
    -I have the forces of Block A as Tension, Normal Force, and Gravity (mg). From my calculations I have that Tension equals 0 (which I don't think is correct) and the Normal Force being equal to 39.2.
    - For Block B I have the forces as Tension and Gravity, which gives me the Tension being equal to 8.82
    - Finally,I separated the tension of the rope on the wall to the x and y components with X: Tcos33 and Y: Tsin33
    - We can assume this is all in static equilibrium. Any advice on mistakes or how to proceed with this problem is much appreciated!

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  2. jcsd
  3. Sep 22, 2015 #2

    billy_joule

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    Look at the just the rope join.

    There are three forces acting, lets call them TA to the left, TB downward, and TW to the right, Θ degrees above horizontal.

    Using ∑Fx = ∑Fy = 0 you can find TW from theta and T B using trig, you don't need to know anything about TA.
     
  4. Sep 22, 2015 #3
    Thank you for the reply. So you're saying that I can't calculate TB By equating the Weight of the block to it?
     
  5. Sep 22, 2015 #4

    billy_joule

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    If it's in static equilibrium then the weight of block A has no effect on TA and is only given to confuse or challenge you, or maybe it's required for a later question.
     
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