Physics Technology Update (4th Edition)

Published by Pearson
ISBN 10: 0-32190-308-0
ISBN 13: 978-0-32190-308-2

Chapter 2 - One-Dimensional Kinematics - Problems and Conceptual Exercises - Page 48: 7


(a) The average speed is less than 20 m/s. (b) More time is spent at 15 m/s than at 25 m/s.

Work Step by Step

$t_{1}$: time spent at 25 m/s. $t_{2}$: time spent at 15 m/s. $10~km=10,000~m$ and $20~km=20,000~m$ $t_{1}=\frac{10,000~m}{25~m/s}=400~s$ $t_{2}=\frac{10,000~m}{15~m/s}=670~s$ $t_{1}+t_{2}=1070~s$ $average~speed=\frac{20,000~m}{1070~s}=19~m/s\lt20~m/s$
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