Physics (10th Edition)

Published by Wiley
ISBN 10: 1118486897
ISBN 13: 978-1-11848-689-4

Chapter 4 - Forces and Newton's Laws of Motion - Problems - Page 119: 102


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 $171.5N$
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