



 
Hi Eric. Let's say x is the number of inches to place the fulcrum from the end that holds the 125 lb. This question concerns torque. The net torque must be zero for the bar to remain steady. So start by drawing a diagram of the forces involved.
Weightless bar: You can see that the lever arms are different lengths in my diagram. Since torque equals force times the lever arm, we have
and must simply solve for x.
Bar with weight: If the bar is not weightless, you need to consider the extra torque applied by the bar acting at its own center of mass (for a uniform bar, this is the midpoint of the bar).
You would need to know the weight of the bar of course. Let's say this is B. Then to balance the torques we have:
And again, we'd solve for x.
Hope this helps,  


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