College Physics (7th Edition)

Published by Pearson
ISBN 10: 0-32160-183-1
ISBN 13: 978-0-32160-183-4

Chapter 2 - Kinematics: Description of Motion - Learning Path Questions and Exercises - Exercises - Page 65: 81


a). $118.61m$ b). time taken $=4.92s$ c). For Lois Lane, $v=48.22m/s$ For Man of Steel, $v=73.8m/s$ These speeds would be fatal for Lois Lane.

Work Step by Step

a). In time t , sum of distances covered by both is equal to 300m. So, Distance by Lois Lane+Distance by Superman=300m. Or, $(0.5\times 9.8t^{2})+(0.5\times15t^{2})=300$ $t=4.92s$ Thus, $h=0.5\times 9.8\times 4.92^{2}=118.61m$ b). time taken $=4.92s$ c). For Lois Lane, $v=u+gt=0+9.8\times 4.92=48.22m/s$ For Man of Steel, $v=0+15\times 4.92=73.8m/s$ Since their relative speed is $48.22+73.8=122m/s$, this would be fatal for Lois Lane.
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