Answer
The force the man exerts on the bar has a magnitude of $171.5N$
Work Step by Step
When the man stands motionless on the scale, the scale shows his exact mass $m=92.6kg$, which means he has a weight of $mg=907.5N$
When the man pulls the bar, there are 3 forces acting on the man:
- The reaction force from the bar $B$
- Normal force $F_N$, which is read by the scale $F_N=75.1\times9.8=736N$
Both $B$ and $F_N$ point upward
- His true weight $mg$, which point downward
As the man has no acceleration, we have $$B+F_N=mg$$ $$B=mg-F_N=907.5-736=171.5N$$
The force he exerts on the bar will have the same magnitude as its reaction force $B$, so it has a magnitude of $171.5N$
