Engineering Mechanics: Statics & Dynamics (14th Edition)

Published by Pearson
ISBN 10: 0133915425
ISBN 13: 978-0-13391-542-6

Chapter 17 - Planar Kinetics of a Rigid Body: Force and Acceleration - Section 17.3 - Equations of Motion: Translation - Problems - Page 438: 41

Answer

$B_y=69.7lb$ $B_x=73.9lb$ $N_A=120lb$

Work Step by Step

We can determine the required normal reactions and acceleration as follows: $\Sigma M_B=\Sigma M_{kB}$ $\implies -N_A\times 13+W\times 10(\frac{12}{13})=ma\times (\frac{5}{13})$ $\implies -N_A\times 13+180\times 10(\frac{12}{13})=\frac{180}{32.2}\times 5\times 10(\frac{5}{13})$ This simplifies to: $N_A=120lb$ We apply the equation of motion in x-direction $\Sigma F_x=ma_x$ $\implies B_x-N_A(\frac{5}{13})=ma$ We plug in the known values to obtain: $B_x-120\times (\frac{5}{13})=\frac{180}{32.2}\times 5$ This simplifies to: $B_x=73.9lb$ Now, we apply the equation of motion in y-direction $\Sigma F_y=ma_y$ $\implies B_y-W+N_A(\frac{12}{13})=0$ We plug in the known values to obtain: $B_y-180+120(\frac{12}{13})=0$ This simplifies to: $B_y=69.7lb$
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