How do I find the tension in the cable from this problem? 
I am trying to find the tension of the cable but I don't know what to do.
 A: You can approach this problem two ways:


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*Balance the forces: Determine a coordinate system you would like to use, draw a free-body diagram, and do some bookkeeping as to which forces are completely or partly along the principle axes of your coordinate system (if partly, use your trig. identities to split up any forces which are in both). We can balance the forces here because there is no net force (acceleration) on the beam if it is in equilibrium. 


$ \sum \vec{F} = 0 $


*

*Balance the torques: Determine a coordinate system (usually choose positive torques to be CCW, but it makes no difference), choose a point of rotation in which to analyze the torques about, and do some bookkeeping. Again, if in equilibrium there is no net torque (rotational acceleration). Note that torque is:


$ \vec{\tau} = \vec{r} \times \vec{F} = rF \sin\theta $
where $r$ is the distance from the pivot point the force is acting, $F$ is the magnitude of the force, and $\theta$ is the angle between the force and radial vector.
A: Assuming system is in equilibrium you can apply condition for rotational equilibrium about A or any other point.
  Equate ( torque of mass of rod from com + torque of weight at the end) with torque of tension.
