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Tension of two strings/picture frame

  1. May 17, 2010 #1
    1. The problem statement, all variables and given/known data
    Hey guys and girls I have tried to solve this one but I got part (b) wrong any help would be awesome :)

    A picture hangs on the wall suspended by two strings, as shown in Figure 6-24, with θ = 72°. The tension in string 1 is 2.0 N

    there is a picture with two strings attached to a ceiling and a picture frame hanging beneath. The θ angle is on string one to the left and string to the right has an angle of 32 degrees.

    a) calculate the force tension of string 2

    b) What is the weight of the picture?

    2. Relevant equations



    3. The attempt at a solution

    Since the forces are at equilibrium, i set net forces = 0.

    the sum of Forces (x) = Force (string 2) - (string 1) = 0
    Sum of Forces (y) = Force tension string 2 + Force tension string 1 - w*g = 0

    I get two equations:
    1) Force tension 1 cos 32 - 2.0 N cos 72 = 0
    2) Force tension 2 sin 32 - 2.0 N sin 72 -(9.80 * w) = 0

    solving for equation 1 i get Force of tension on string 2 = 0.7288 N which comes out as correct

    However, I get part b) weight of the picture wrong

    I put my Force of tension 2 into equation 2 to get weight

    (0.5299)(0.7288) + 1.902 -9.80*w = 0
    solving i get weight = 0.2335 N but that comes out as wrong. Help lol
     
  2. jcsd
  3. May 17, 2010 #2

    kuruman

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    Gold Member

    Why the negative sign here? Aren't both vertical components of the tensions positive? Also, why are you multiplying the weight by 9.8?
     
    Last edited: May 17, 2010
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