Help: Newton's Laws - cement bag at rest.

AI Thread Summary
A cement bag weighing 339 N is suspended from three wires, and the system is in equilibrium. The user has correctly identified T3 as 339 N and created a free-body diagram to resolve forces into their x and y components. They derived two equations for equilibrium but struggled to solve for T1 after substituting T2 into the second equation. Another participant confirmed the approach was correct and suggested rewriting the equation to isolate T1, making it solvable. The discussion emphasizes the importance of correctly applying Newton's Laws and resolving forces in equilibrium problems.
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Q: A bag of cement of weight 339 N hangs from three wires as suggested in the figure below. Two of the wires make angles and with the horizontal. If the system is in equilibrium, find the tensions in the wires?

pse6e.05.18p.e.jpg


The answer requires T1, T2, T3.

I know T3 = Fgravity = 339N.

I made a free-body diagram at the knot:

http://www.njsr.org/pics/albums/userpics/fbd.GIF

Now, I can resolve the forces into their x, y components:

T1: x: -T1(cos62) y: T1(sin62)
T2: x: T2(cos25) y: T2(sin25)
T3: x: 0 y: -339N

I can make the two required equations:

(1) Fnetx = T2(cos25) - T1(cos62) = 0

(2) Fnety = T1(sin62) + T2(sin25) - 339 = 0

I can solve (1) for T2 in terms of T1:

T2 = T1(cos62/cos25)
T2 = 0.961 T1

My problem occurs here, substituting T2 into (2) to get T1:

T1(sin62) + (0.961 T1)(sin25) - 339 = 0

I do not know how to solve for T1. Could someone be of assistance, and also double check that I got everything up until the point I was stuck, correct?

Thank you!

PS. This is first-year University Physics.
 
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Now, I haven't bothered to check your numerical values; your approach has no flaws as far as I can see.
"T1(sin62) + (0.961 T1)(sin25) - 339 = 0"
Rewrite this as:

T1(sin62 + 0.961sin25) = 339
You should be able to solve it now.
 
That helps tremendously. Thank you very much!
 
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