Engineering Mechanics: Statics & Dynamics (14th Edition)

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

Chapter 20 - Three-Dimensional Kinematics of a Rigid Body - Section 20.3 - General Motion - Problems - Page 572: 4

Answer

$$ \begin{aligned} & \mathbf{v}_A=\{-5.20 \mathbf{i}-12 \mathbf{j}+20.8 \mathbf{k}\} \mathrm{ft} / \mathrm{s} \\ & \mathbf{a}_A=\{-3.33 \mathbf{i}-21.3 \mathbf{j}+6.66 \mathbf{k}\} \mathrm{ft} / \mathrm{s}^2 \end{aligned} $$

Work Step by Step

$$ \begin{aligned} \mathbf{r}_{A I O}= & 40 \cos 30^{\circ} \mathbf{j}+40 \sin 30 \mathbf{k} \\ \mathbf{r}_{A O O}= & \{34.641 \mathbf{j}+20 \mathbf{k}\} \mathrm{ft} \\ \Omega= & \omega_1 \mathbf{k}+\omega_2 \mathbf{i}=\{0.6 \mathbf{i}+0.15 \mathbf{k}\} \mathrm{rad} / \mathrm{s} \\ \dot{\omega}= & \dot{\omega}_1 \mathbf{k}+\dot{\omega}_2 \mathbf{i}+\omega_1 \mathbf{k} \times \omega_2 \mathbf{i} \\ \dot{\Omega}= & 0.2 \mathbf{k}+0.4 \mathbf{i}+0.15 \mathbf{k} \times 0.6 \mathbf{i}=\{0.4 \mathbf{i}+0.09 \mathbf{j}+0.2 \mathbf{k}\} \mathrm{rad} / \mathrm{s}^2 \\ \mathbf{v}_A= & \Omega \times \mathbf{r}_{A O}=(0.6 \mathbf{i}+0.15 \mathbf{k}) \times(34.641 \mathbf{j}+20 \mathbf{k}) \\ \mathbf{v}_A= & \{-5.20 \mathbf{i}-12 \mathbf{j}+20.8 \mathbf{k}\} \mathrm{ft} / \mathrm{s} \\ \mathbf{a}_A= & \Omega \times\left(\Omega \times \mathbf{r}_{A O}\right)+\dot{\omega} \times \mathbf{r} \mathbf{r}_{A O} \\ \mathbf{a}_A= & (0.6 \mathbf{i}+0.15 \mathbf{k}) \times[(0.6 \mathbf{i}+0.15 \mathbf{k}) \times(34.641 \mathbf{j}+20 \mathbf{k})] \\ & +(0.4 \mathbf{i}+0.09 \mathbf{j}+0.2 \mathbf{k}) \times(34.641 \mathbf{j}+20 \mathbf{k}) \\ \mathbf{a}_A= & \{-3.33 \mathbf{i}-21.3 \mathbf{j}+6.66 \mathbf{k}\} \mathrm{ft} / \mathrm{s}^2 \end{aligned} $$
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