University Physics with Modern Physics (14th Edition)

Published by Pearson
ISBN 10: 0321973615
ISBN 13: 978-0-32197-361-0

Chapter 5 - Applying Newton's Laws - Problems - Exercises - Page 164: 5.54

Answer

(a) $v = 5.24~m/s$ (b) At the highest point, the apparent weight is 833 N. At the lowest point, the apparent weight is 931 N. (c) One revolution would take 14.2 seconds. (d) At the lowest point, the apparent weight is 1760 N.

Work Step by Step

(a) $v = \frac{2\pi ~r}{t} = \frac{(2\pi)(50~m)}{60~s}$ $v = 5.24~m/s$ (b) Note that the apparent weight is equal to the normal force $F_N$ exerted on the passenger by the seat. At the highest point: $\sum F = \frac{mv^2}{r}$ $mg - F_N = \frac{mv^2}{r}$ $F_N = mg - \frac{mv^2}{r}$ $F_N = 882~N - \frac{(882~N)(5.24~m/s)^2}{(9.80~m/s^2)(50~m)}$ $F_N = 833~N$ At the lowest point: $\sum F = \frac{mv^2}{r}$ $F_N - mg = \frac{mv^2}{r}$ $F_N = mg + \frac{mv^2}{r}$ $F_N = 882~N + \frac{(882~N)(5.24~m/s)^2}{(9.80~m/s^2)(50~m)}$ $F_N = 931~N$ (c) $mg = \frac{mv^2}{r}$ $v = \sqrt{gr}$ We can find the time $T$ for one revolution. $T = \frac{2\pi ~r}{v} = 2\pi~\sqrt{\frac{r}{g}}$ $T = 2\pi~\sqrt{\frac{50~m}{9.80~m/s^2}}$ $T = 14.2~s$ (d) At the lowest point: $\sum F = \frac{mv^2}{r}$ $F_N - mg = \frac{mv^2}{r}$ $F_N = mg + \frac{mv^2}{r}$ $F_N = 882~N + \frac{(882~N)(9.80~m/s^2)(50~m)}{(9.80~m/s^2)(50~m)}$ $F_N = 1760~N$
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