Calculus 8th Edition

Published by Cengage
ISBN 10: 1285740629
ISBN 13: 978-1-28574-062-1

Chapter 13 - Vector Functions - 13.4 Motion in Space: Velocity and Acceleration - 13.4 Exercises - Page 919: 40

Answer

$4e^{2t},2e^{t}$

Work Step by Step

Tangential acceleration component can be calculated as: $a_T=\dfrac{r'(t) \cdot r''(t)}{|r'(t)|}$ Normal acceleration component can be calculated as: $a_N=\dfrac{r'(t) \times r''(t)}{|r'(t)|}$ From the question, $r'(t)= i+2e^tj+2e^{2t}k$ and $r''(t)=2e^tj+4e^{2t}k$ This yields,$|r'(t)|=\sqrt{(1)^2+(2e^t)^2+(2e^{2t})^2}=1+2e^{2t}$ Thus, $r'(t) \cdot r''(t)=[i+2e^tj+2e^{2t}k] \cdot [2e^tj+4e^{2t}k]=4e^{2t}(1+2e^t)$ Also, $|r'(t) \times r''(t)|=[i+2e^tj+2e^{2t}k] \times [2e^tj+4e^{2t}k]=2e^{t}(1+2e^t)$ After simplifications, we get $a_T=\dfrac{r'(t) \cdot r''(t)}{|r'(t)|}=\dfrac{4e^{2t}(1+2e^t)}{1+2e^{2t}}$ or, $=4e^{2t}$ Now, $a_N=\dfrac{|r'(t) \times r''(t)|}{|r'(t)|}$ or, $=\dfrac{2e^{t}(1+2e^t)}{1+2e^{2t}}$ or, $=2e^{t}$
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