Essential University Physics: Volume 1 (4th Edition)

Published by Pearson
ISBN 10: 0-134-98855-8
ISBN 13: 978-0-13498-855-9

Chapter 12 - Exercises and Problems - Page 222: 25

Answer

No. The climber only got $90\%$ of the way across the log

Work Step by Step

Please see the attached image first. Let's consider the static equilibrium of the board. $\uparrow \sum \vec F=0$ $n_{1}-m_{1}g-m_{2}g=0$ $n_{1}=(m_{1}+m_{2})g-(1)$ $\rightarrow \sum\vec F=0$ $F_{S}-n_{1}=0$ $F_{S}=n_{2}-(2)$ $\sum \tau_{A}\curvearrowright=0$ $m_{1}g\frac{L}{3}cos26^{\circ} + m_{2}gxcos26^{\circ}\space -n_{2}Lsin26^{\circ}=0$ $(2)=\gt(3)$ $m_{1}g\frac{L}{3}cos26^{\circ} + m_{2}gxcos26^{\circ}\space -F_{S}Lsin26^{\circ}=0$ $\frac{m_{1}gcot26^{\circ}}{3}+\frac{m_{2}gxcot26^{\circ}}{L}=F_{S}-(4)$ Let's apply x = L $\frac{m_{1}gcot26^{\circ}}{3}+\frac{m_{2}gcot26^{\circ}}{L}=F_{S}$ $\frac{(224g+77.3g)}{3}\times2.05=F_{S}$ $311.53g=F_{S}-(A)$ Now let's find the maximum static friction of the horizontal wall. $F_{S}=\mu n_{1}= 0.982(m_{1}+m_{2})g$ $F_{S}= 295.88g-(B)$ $(A)\gt (B)$ , So the climber can't get to the righthand end of the log. $(B), (4)=\gt$ $(\frac{m_{1}}{3}+\frac{m_{2}x}{L})gcot26^{\circ}=295.88g$ $77.3\frac{x}{L}=144.31-\frac{224}{3}=0.9L$ The climber can only get $90\%$ of the way across the log.
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