Thermodynamics: An Engineering Approach 8th Edition

Published by McGraw-Hill Education
ISBN 10: 0-07339-817-9
ISBN 13: 978-0-07339-817-4

Chapter 2 - Energy, Energy Transfer, and General Energy Analysis - Problems - Page 99: 2-30

Answer

$E=685.66kJ$

Work Step by Step

Here we have to kind of work, the one to change the potential energy and the one to change the kinetic energy: $W=\Delta E$ First we are going to calculate the work to change the potential energy: $W_{p}=mg\Delta z=mg(z_{2}-z_{1})=1300kg*9.81\frac{m}{s^2}*(40m-0m)=510120J$ And now the work to change the kinetic energy: $W_{k}=\frac{m}{2}\Delta V^2=\frac{m}{2}(V_{2}^2-V_{1}^2)=\frac{1300kg}{2}*[((60\frac{km}{h}*(\frac{1000m}{1km})*(\frac{1h}{3600s}))-((10\frac{km}{h})*(\frac{1000m}{1km})*(\frac{1h}{3600s}))]=175540.12J$ Then the total energy needed is: $E= W_{t}=W_{p}+W_{k}=510.12kJ+175.54kJ=685.66kJ$
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