Tension of two strings/picture frame

1. May 17, 2010

P944

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. May 17, 2010

kuruman

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