How do you determine 'r' in Torque calculations?

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In torque calculations, 'r' represents the distance from the pivot point to the point of force application. The discussion highlights confusion regarding the determination of 'r', specifically when it is expressed as L*cos(phi). The geometry of the situation is questioned, particularly the ability to solve for 'r' with limited information from the triangle formed. It is suggested that additional angles, such as the one between the rope and the bar, could aid in clarifying the calculation. Understanding these geometric relationships is crucial for accurately determining 'r' in torque equations.
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Homework Statement


8GcR8.png



Homework Equations


Torque = r * F * sin(x)


The Attempt at a Solution


The solution says that the 'R' I marked was L*cos(phi). I fail to see the geometry of how they got this...you have only one side and one right angle for that triangle...how can you solve for 'R'?
 
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PhizKid said:
you have only one side and one right angle for that triangle...
You should be able to find the other angles, for example between the right hand rope and the bar.
 

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