Physics for Scientists and Engineers: A Strategic Approach with Modern Physics (3rd Edition)

Published by Pearson
ISBN 10: 0321740904
ISBN 13: 978-0-32174-090-8

Chapter 19 - Heat Engines and Refrigerators - Exercises and Problems - Page 551: 40

Answer

$98\;\rm cycle$

Work Step by Step

We know that the thermal efficiency of the Carnot engine is given by $$\eta_{\rm Carnot}=1-\dfrac{T_C}{T_H}$$ which is also given by $$\eta_{\rm Carnot}=\dfrac{W_{\rm out}}{Q_H}$$ Thus, $$1-\dfrac{T_C}{T_H}=\dfrac{W_{\rm out}}{Q_H}$$ Thus the work done in one cycle is given by $${W_{\rm out}}=Q_H\left[1-\dfrac{T_C}{T_H}\right]\tag 1$$ And the total work needed to raise the 10-kg mass a 10 m up is given by $$W=F_g\Delta y=mgh\tag 2$$ Hence, the number of cycles needed to raise the mass is given by $$N=\dfrac{W}{{W_{\rm out}}}$$ Plugging from (1) and (2); $$N=\dfrac{mgh}{Q_H\left[1-\dfrac{T_C}{T_H}\right]}$$ Plugging the known; $$N=\dfrac{(10)(9.8)(10)}{(25)\left[1-\dfrac{0+273}{182+273}\right]}$$ $$N=\color{red}{\bf 98}\;\rm cycle$$
Update this answer!

You can help us out by revising, improving and updating this answer.

Update this answer

After you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.