# Equilibrium Force?

## Homework Statement

34. Joe wishes to hang a soign weighing 750N so that cable A attached to the store makes a 30 degrees angle, as shown in Figure 7-16. Cable B is horizontal and attached to an adjoining building. What is the tension in Cable B.

Figure 7-16 was roughly sketched in Paint from the textbook. All pertinent information is presented.

## The Attempt at a Solution

Well, my only attempt to a solution was, first: Do The square root of 750cos30^2 +750sin30^2. This simply lead me to getting 750N as my answer. Well, I did that for 750cos0 etc, following same procedure, and answer is 750N. I did it for 750cos120 and I still got the same answer( 120 because thats the angle between A-B). I really don't think the answer is 750 because wouldn't the force split between both wires.. Unless A would be the only thing holding the sign up, but then the sign would.. crash into the left building. Umm.. I really dont know what else I can do to solve it, so if u could give me a hand? Thanks

** Sorry for the misleading title, I was gonna present another problem but then i figured out how to do it and moved on, and yet sturggled with another one so I just had the page open and presented the problem, yet forgot to change its title, which is still a little pertinent to what its about.

#### Attachments

• physics sketch.bmp
95.1 KB · Views: 460
Last edited:

robb_
Sorry, cant see your sketch yet.
Draw a free body diagram for the sign. Is it accelerating?

Sorry, cant see your sketch yet.
Draw a free body diagram for the sign. Is it accelerating?

Well the sketch is basically just two buildings

||||\ .
||||-\
||||30\ Wire A
||||---\
||||----\ ______________________
!!!!!!!--------- Wire B (above)
!!!!!!!| Rob's | (just imagine exclamation marks are not there)
!!!!!!!---------

Its not accelerating

- The sketch is attached to the first post

Free body diagram?

After I draw the free body diagram what should I do?

robb_
Choose a coordinate system and then break up the force vectors into components. Write down F_net = ma for each direction, and you just said a is zero, so what does that imply for F_net in either direction?