Calculus: Early Transcendentals 9th Edition

Published by Cengage Learning
ISBN 10: 1337613924
ISBN 13: 978-1-33761-392-7

Chapter 3 - Section 3.7 - Rates of Change in the Natural and Social Sciences - 3.7 Exercises - Page 237: 31

Answer

a) $v(0)=0.925$$cm^2/s$ $v(0.005)=0.694$ $cm^2/s$ $v(0.01)=0$$cm^2/s$ b) $v'(0)=0$ $v'(0.005)=-92.592$ cm/s/cm $v'(0.01)=-185.185 $ $cm^2/s$ c) The velocity is greater at $r=0$ and changing most at $R=0.01$

Work Step by Step

(a) Find the velocity of the blood along the center-line $r − 0$, at radius $r − 0.005$ cm, and at the wall $r − R − 0.01$ cm. solution:- By using $v=\frac{p}{4{\eta}l}(R^2-r^2)$ Where $R=0.01, l=3,p=3000, {\eta}=0.027$ Now we have a function, $v(r)=\frac{p}{4{\eta}l}(R^2-r^2)$ $v(r)=\frac{3000}{4(0.027)3}((0.01)^2-r^2)$ $v(0)=\frac{1000}{4(0.027)3}((0.01)^2-r^2)$ $v(0)=0.925$cm/s/cm $v(0)=0.925$$cm^2/s$ $v(0.005)=0.694$ cm/s/cm $v(0.005)=0.694$ $cm^2/s$ $v(0.01)=0$ cm/s/cm $v(0.01)=0$$cm^2/s$ b) As we know we have a function ; $v(r)=\frac{p}{4{\eta}l}(R^2-r^2)$ Taking differentiate w.r.t $r$ on both sides $v'(r)=\frac{d}{dr}(\frac{p}{4{\eta}l}(R^2-r^2))$ $v'(r)=(\frac{P}{4{\eta}l})\frac{d}{dr}(R^2-r^2)$ $v'(r)=(\frac{P}{4{\eta}l)})(\frac{d}{dr}(R^2)-\frac{d}{dr}(r^2))$ $v'(r)=(\frac{P}{4{\eta}l)})(-2r)$ $v'(r)=-\frac{Pr}{2{\eta}l}$ We have $R=0.01, l=3,p=3000, {\eta}=0.027$ so, $v'(r)=\frac{3000r}{2(0.027)3}$ $v'(0)=\frac{3000{\times}(0)}{2(0.027)3}$ $v'(0)=0$ $v'(0.005)=\frac{3000{\times}(0.005)}{2(0.027)3}$ $v'(0.005)=-92.592$ cm/s/cm $v'(0)=-92.592$ $cm^2/s$ $v'(0.01)=\frac{3000{\times}(0.01)}{2(0.027)3}$ $v'(0.01)=-185.185 $ cm/s/cm $v'(0.01)=-185.185 $ $cm^2/s$ c) The velocity is greater at $r=0$ and changing most at $R=0.01$
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