Calculus, 10th Edition (Anton)

Published by Wiley
ISBN 10: 0-47064-772-8
ISBN 13: 978-0-47064-772-1

Chapter 4 - Integration - 4.7 Rectilinear Motion Revisited Using Integration - Exercises Set 4.7 - Page 329: 10

Answer

$ \text {(a) Displacement = 2m and Distance = $\frac{10}{3}$}$ $ \text {(b) Displacement = $\frac{10}{4}$ and Distance = $\frac{10}{4}$}$

Work Step by Step

$ \text {Given the velocity and the time period and displacement/distance is unknown.} $ $ \text {(a)}$ \begin{align} v(t) = 3t -2; \ 0\leq t \leq2 \end{align} $ \text {Displacement:}$ \begin{align} s(t) = \int_{0}^{2} (3t-2) \ dt = \left[{\frac{3t^2}{2}} - 2t\right]_{0}^{2} = 2 m \end{align} $ \text {Distance:}$ \begin{align} d(t) = \int_{0}^{2} |3t-&2| \ dt = \int_{0}^{\frac{2}{3}} (-3t+2) \ dt \ + \int_{\frac{2}{3}}^{2} (3t-2) \ dt = \\ & = \left[{-\frac{3t^2}{2}} + 2t\right]_{0}^{\frac{2}{3}} + \left[{\frac{3t^2}{2}} - 2t\right]_{\frac{2}{3}}^{2} = \frac{2}{3} + \frac{8}{3} = \frac{10}{3} \end{align} $\text{(b)}$ \begin{align} v(t) = |1-2t|; \ 0\leq t \leq2 \end{align} $ \text {Displacement:}$ \begin{align} s(t) = \int_{0}^{2} |1-&2t| \ dt = \int_{0}^{\frac{1}{2}}(1-2t) \ dt + \int_{\frac{1}{2}}^{2} (-1+2t) \ dt = \\ & = \left[t - t^2 \right]_{0}^{\frac{1}{2}} + \left[-t + t^2 \right]_{\frac{1}{2}}^{2} = \frac{1}{4} + \frac{9}{4} = \frac{10}{4} \end{align} \begin{align} d(t) = \int_{0}^{2} |1-&2t| \ dt = \int_{0}^{\frac{1}{2}}(1-2t) \ dt + \int_{\frac{1}{2}}^{2} (-1+2t) \ dt = \\ & = \left[t - t^2 \right]_{0}^{\frac{1}{2}} + \left[-t + t^2 \right]_{\frac{1}{2}}^{2} = \frac{1}{4} + \frac{9}{4} = \frac{10}{4} \end{align}
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