Calculus (3rd Edition)

Published by W. H. Freeman
ISBN 10: 1464125260
ISBN 13: 978-1-46412-526-3

Chapter 17 - Line and Surface Integrals - 17.2 Line Integrals - Exercises - Page 934: 54

Answer

The work done by the field along the given path is $2{\rm{e}} - \frac{{39}}{{20}}$.

Work Step by Step

We obtain ${\bf{F}}\left( {{\bf{r}}\left( t \right)} \right) = \left( {{{\rm{e}}^{{t^2}}},{{\rm{e}}^t},\frac{{{t^4}}}{2}} \right)$ ${\bf{r}}'\left( t \right) = \left( {2t,1,\frac{1}{2}} \right)$ The work done by the field: $W = \mathop \smallint \limits_C^{} {\bf{F}}\cdot{\rm{d}}{\bf{r}} = \mathop \smallint \limits_0^1 {\bf{F}}\left( {{\bf{r}}\left( t \right)} \right)\cdot{\bf{r}}'\left( t \right){\rm{d}}t$ $W = \mathop \smallint \limits_0^1 \left( {{{\rm{e}}^{{t^2}}},{{\rm{e}}^t},\frac{{{t^4}}}{2}} \right)\cdot\left( {2t,1,\frac{1}{2}} \right){\rm{d}}t$ $ = \mathop \smallint \limits_0^1 \left( {2t{{\rm{e}}^{{t^2}}} + {{\rm{e}}^t} + \frac{{{t^4}}}{4}} \right){\rm{d}}t$ $ = \mathop \smallint \limits_0^1 {{\rm{e}}^{{t^2}}}{\rm{d}}\left( {{t^2}} \right) + \mathop \smallint \limits_0^1 {{\rm{e}}^t}{\rm{d}}t + \frac{1}{4}\mathop \smallint \limits_0^1 {t^4}{\rm{d}}t$ $ = \left( {{{\rm{e}}^{{t^2}}}|_0^1 + {{\rm{e}}^t}|_0^1 + \frac{1}{{20}}{t^5}|_0^1} \right)$ $ = {\rm{e}} - 1 + {\rm{e}} - 1 + \frac{1}{{20}} = 2{\rm{e}} - \frac{{39}}{{20}}$ So, the work done by the field along the given path is $2{\rm{e}} - \frac{{39}}{{20}}$.
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