How Do You Calculate Cable Tension in a Bird Feeder Setup?

[xcgirl]

Homework Statement

A 168 N bird feeder is supported by three cables, as shown in Figure P4.17. Find the tension in each cable.

picture can be found here: http://www.webassign.net/sf5/p4_13.gif

Homework Equations

all trig functions

The Attempt at a Solution

left cable:
sin(60) = 168/T
T = 336

this did not work when i put in the answer on webassign so i didnt even try for the right cableI think I'm doing something fundamentally wrong.

 

[Astronuc]

The vertical cable should be straightforward. It bears the entire weight of the bird house (including whatever bird(s) and food happen to be supported by it).

The two diagonal cables have to be resolved into horizontal and vertical components.

The horizontal components must be equal and opposite (i.e. one force is the opposite of the other).

The sum of the vertical components must equal _________________?

Please write the equations for the horizontal and vertical net forces for the diagonal cables.


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