University Physics with Modern Physics (14th Edition)

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

Chapter 2 - Motion Along a Straight Line - Problems - Exercises - Page 63: 2.66

Answer

Distance covered by me before I catch the bus = 74.138m My speed at that moment = 11.93m/s No an average college student will not be able to catch, World record of Usain Bolt is that of 10.44 m/s Average man runs with speed of 6-8m/s

Work Step by Step

Let us first calculate the time taken to catch the bus I have cover distance of 12m plus whatever distance the bus moves subsequently after I start running. So, Distance moved by bus in time t = $5t$ Distance covered by me in time t = $\frac{1}{2}at^{2} = \frac{1}{2}(0.96)t^{2}$ To catch the bus, $12+5t = \frac{1}{2}(0.96)t^{2}$ Solving the quadratic equation gives $t = 12.428, -2.011$ Time can not be negative so -2.011 sec neglected So distance covered before bus is caught = $\frac{1}{2}(0.96)(12.428)^{2} = 74.138 m$ My speed at that moment would be $v = at = 0.96*12.428 = 11.93m/s$ No an average college student will not be able to achieve this. World record of fastest speed by Usain Bolt is of 10.44m/s
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