How do I find the tension in two cables holding up a sign at a 50 degree angle?

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Homework Help Overview

The problem involves determining the tension in two cables supporting a sign with a mass of 100 kg, which is suspended at a 50-degree angle from the horizontal. The weight of the sign is calculated using the equation w = m * g, leading to a weight of 980 N. Participants are exploring the implications of equilibrium and the forces acting on the sign.

Discussion Character

  • Exploratory, Conceptual clarification, Problem interpretation

Approaches and Questions Raised

  • Participants discuss the calculation of weight and the importance of equilibrium, questioning the net force on the sign. They suggest drawing a free body diagram to visualize the forces involved, including the vertical components of the tension forces.

Discussion Status

The discussion is ongoing, with participants providing guidance on drawing free body diagrams and emphasizing the need to consider the forces acting on the sign. There is an acknowledgment of the need for clarity regarding the vertical components of the tension forces.

Contextual Notes

Participants are working under the constraints of a homework assignment and are focused on understanding the problem rather than arriving at a final solution. There is a noted typo in the weight calculation that has been clarified during the discussion.

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Homework Statement


I am reviewing for a test tomorrow and cannot figure this problem out. A sign with the mass of 100kg hangs from the ceiling. If the two cables that are attach the sign to the ceiling are at a 50 degree angle from the horizontal, what is the tension in each cable? The answer is 640N, but i don't know why?

Homework Equations


w=m*g

The Attempt at a Solution


I understand that w=m*g, and i found that w=931N, However i have no idea what to do from here.
 
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joshuajen said:
I understand that w=m*g, and i found that w=931N,
Recheck your math. What did you use for g?

However i have no idea what to do from here.
Draw yourself a free body diagram of the sign including all the forces acting on it.

If the sign is in equilibrium, what must be the net force on it?
 
first the calculations was a typo i meant to say 980. secondly i understand that the net force should be zero. This problem still makes no sense to me.
 
joshuajen said:
first the calculations was a typo i meant to say 980. secondly i understand that the net force should be zero.
Good.

This problem still makes no sense to me.
Did you draw a free body diagram of the sign? What forces act on the sign? What are their vertical components?
 
ok, so i drew the free body diagram and the only things i was the angles of the two and the weight.
 
joshuajen said:
ok, so i drew the free body diagram and the only things i was the angles of the two and the weight.
I assume you mean that the only forces acting are the two tensions, which act upward at an angle, and the weight.

So if you call the tension in each cable T, what is the vertical component of that tension force?
 

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