Law of Sines for Tension?

In summary, the conversation discusses a problem involving a chandelier supported by two ropes at different angles. The tension in the second rope and the mass of the chandelier are unknown. The attempt at a solution involved using the law of sines, but resulted in significantly different answers from what the professor said they should be. After drawing a diagram and simplifying the problem, the correct answers were found using right angle trigonometry. The tension in the second rope was found to be 178.8N and the mass of the chandelier was 23.8kg.
  • #1
CandyApples
28
0

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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  • #2
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 .
 
  • #3
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 :).
 

What is the Law of Sines for Tension?

The Law of Sines for Tension is a mathematical relationship that describes the relationship between the tension in a string or cable and the angles at which it is pulled. It states that the ratio of the sine of an angle to the length of the string is equal to the ratio of the sine of the opposite angle to the length of the string.

How is the Law of Sines for Tension used?

The Law of Sines for Tension is used in various fields, such as engineering and physics, to calculate the tension in a string or cable when given the angle at which it is pulled and the length of the string. It is also used in solving problems involving forces and equilibrium.

What are the limitations of the Law of Sines for Tension?

The Law of Sines for Tension assumes that the string or cable is perfectly flexible and has no weight, and that the angles are measured in radians. It also assumes that the tension is constant throughout the string. These assumptions may not hold true in certain real-life situations and can affect the accuracy of the calculations.

Can the Law of Sines for Tension be used in non-right triangles?

Yes, the Law of Sines for Tension can be used in any triangle, whether it is a right triangle or not. It can also be used in triangles with more than three sides, as long as the angles and lengths of the sides are known.

Are there any other laws or equations related to the Law of Sines for Tension?

Yes, the Law of Sines for Tension is closely related to the Law of Cosines and the Pythagorean theorem. These laws and equations can be used together to solve more complex problems involving forces and tensions in strings and cables.

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