Equilibrium of three suspended blocks

[Phys121VIU]

Homework Statement

http://imageshack.us/photo/my-images/851/45009287.png/

The problem(s) are shown in the link, but I'm having trouble getting them started.

Homework Equations

The Attempt at a Solution

For 3-12:

I think what I need to do is find the tension force in the ropes leading from each block to point A. Then with those forces I find the Sum of the forces in X and Y

From there i think i know what to do, its just that i don't know how to find the force in each rope!

My attempt:

For block B, the force in the the rope to point A is sin∅/200lb. For block C, the force in the rope to point a is sin(30)/100 =50lb .

Is this correct so far?

 

[Doc Al]

For block B, the force in the the rope to point A is sin∅/200lb. For block C, the force in the rope to point a is sin(30)/100 =50lb .

Is this correct so far?

No. First things first. What's the tension in the rope connecting to B and the rope connecting to C? Hint: No calculation is required. (Consider the forces on B and C.) Then you can worry about the force components acting on point A.

Careful how you write things: don't confuse sin(30)/100 with 100*sin(30).

 

[Phys121VIU]

What's the tension in the rope connecting to B and the rope connecting to C?

I got it figured out, I was definitely over thinking it.

The tension in the ropes are equal to the weight of the blocks, so rope AB is 200lb and AC is 100lb.

Then I find the Sum of forces for X and Y and solve for the unknowns!

Thanks!