# Homework help- tension

1. Nov 12, 2007

### liz155

Joe wishes to hang a sign weighing 775 N so that cable A attached to the store makes a 30.0° angle, as shown in Figure 7-16. Cable B is horizontal and attached to an adjoining building.

I have no idea where to start. Thanks for any help. :-)

--Cori

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2. Nov 12, 2007

Draw a Free Body Diagram and then begin with summing the forces in the x and y directions, and possibly taking a moment too.

3. Nov 12, 2007

### liz155

Sorry, I still don't understand. Could you maybe explain in more detail? I attached a picture of the diagram in my book if that helps. :-)

4. Nov 13, 2007

### catkin

5. Nov 13, 2007

### andrevdh

Since the sign is in equilibrium the sum of the components of the forces need to be zero.
Can you set the two equations up for the horizontal and vertical components of the forces? I assume that you need to determine the tensions in the cables.

6. Nov 14, 2007

### jw2007

What are you solving for specifically? Are you looking for tension in the cables. If so, I believe you can probably start with something like this:

Do you free body diagram and for the equations consider the ones below:

Fx=Fsin(theta)
Fy=Fcos(theta)

I believe since you know the sign is 775N you have a starting point there. You can start with cable A and substitute what you know for A in place of F. You already have Theta (the angle). This should get you going.

7. Nov 15, 2007

### liz155

Thanks for all the help everyone! I finally got the answer, and when I checked with my teacher..... it was right!

Thanks!