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 53: 75

Answer

(a) $8.4~m/s$ in the positive direction (upward). (b) $1.4~m/s$ in the negative direction (downward).

Work Step by Step

(a) We know that $v=v_i-gt$ We plug in the known values to obtain: $v=28m/s-(9.81m/s^2)(2s)$ $\implies v=8.4m/s$ upward (b) As $v=v_i-gt$ We plug in the known values to obtain: $v=28m/s-(9.81m/s^2)(3s)$ $v=-1.4m/s$ The negative sign shows that the speed is directed downward.
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