Heres a tough sign question with equilibrium that will be on the test.

[davie08]

Homework Statement

A sign that weighs 168N is supported by 2 ropes, a and b, that make 22.5 degree angles with the horizontal. The sign is not moving, what forces do the ropes exert on the sign. I have 45 minutes to figure this out.

Homework Equations

I don't know any equations

The Attempt at a Solution

I don't no where to start

 

[dx]

Let the tension in the ropes have magnitude T. What is the expression for the vertical component of the tension in each rope? What is the total vertical force on the sign due to the ropes in terms of T? What value must this force have to balance the weight of the sign?

 

[davie08]

ok I don't understand that can you show me the first step through the numbers.

 

[dx]

Which part don't you understand?

 

[davie08]

I don't know I am bad with this kind of stuff

 

[dx]

Do you know what tension is? Which direction is it pointing in? Do you know how to use the trigonometric functions to find the components of vectors?

For example, if a vector is pointing in a direction 10 degrees above the horizontal, and has magnitude 50, it has a horizontal component 50cos(10). Are you familiar with this sort of thing?

 

[Andrew Mason]

Homework Statement

A sign that weighs 168N is supported by 2 ropes, a and b, that make 22.5 degree angles with the horizontal. The sign is not moving, what forces do the ropes exert on the sign. I have 45 minutes to figure this out.

Homework Equations

I don't know any equations

The Attempt at a Solution

I don't no where to start

By symmetry you can see that there should be no difference between the magnitude of the tension force in each of the two ropes.

What is the downward force? Does the sign accelerate? So what can you tell about the net vertical force (downward - upward)? So what is the sum of the upward components of tension in the ropes? What does that tell you about the magnitude of the tensions in the ropes? What is the net horizontal force on the sign? (ie. does it accelerate sideways?). What are the horizontal components of the tension forces?

AM

 

[davie08]

ok I have to go I am going to try and ask my teacher about this question before I write it.