Can the Law of Sines Determine Chandelier Tension Accurately?

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SUMMARY

The discussion centers on the application of the Law of Sines to determine the tension in ropes supporting a chandelier. The user initially calculated the tension in rope 2 as 125.86N, while the correct value is 179N. The mass of the chandelier was found to be 19.66kg instead of the correct 23.8kg. The discrepancy arose from the inappropriate use of the Law of Sines, which was resolved by employing right-angle trigonometry and breaking the problem into two right triangles.

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  • Understanding of basic trigonometry, specifically the Law of Sines
  • Knowledge of Newton's second law of motion (F = ma)
  • Ability to draw and interpret free-body diagrams
  • Familiarity with resolving forces into components (Fx and Fy)
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  • Study the application of right-angle trigonometry in physics problems
  • Learn how to draw and analyze free-body diagrams for complex systems
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Homework Statement


A large chandelier is supported by two ropes. Rope 1 makes a 40 degree angle with the ceiling and has a tension of 150N. Rope two forms a 50 degree angle with the ceiling. What is the tension in rope 2 and what is the mass of the chandelier given the chandelier.


Homework Equations


F = ma
T-mg = ma
Law of sines?

The Attempt at a Solution


So i solved it through the law of sines and got an answer significantly different than what my professor said it should be. I would be interested in knowing why.
Here is the work:
150/sin(50) = T2/sin40
T2 = 150*sin(40)/sin(50)
T2 = 125.86N whereas the correct answer is 179N.

Then for the mass:
150*sin(40)+125.86*sin(50) = mg
m = 19.66kg whereas the correct answer is 23.8kg.

I was wondering why the law of sines did not provide a correct answer in this case, and what different steps I should take to get at the right answer. Thanks in advance!
 
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Is there any particular reason you are using the law of sines? Draw a picture, how can you divide the triangle into two right triangles? Once you do this it is simple right angle trigonometry .
 
My apologies, I overcomplicated this problem. Upon drawing a diagram it is obvious Fx = T2cos(50) - 150cos(40). Fy = T2sin50 + 150sin40. Apply second law to Fx and force comes out nicely to 178.8N, plug that into Fy and it is in fact 23.8kg. Thanks for the help :).
 

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