Answer
39.2 m/s up
Work Step by Step
Let up be the positive direction
$x=ut+\frac{1}{2}at^{2}$
$u=\frac{x-\frac{1}{2}at^{2}}{t}$
$u=\frac{0-\frac{1}{2}(-9.8)(8.0)^{2}}{(8.0)}=39.2\; m/s$
Hence, the initial velocity is 39.2 m/s up.
Physics (10th Edition)
by Young, David; Stadler, Shane
Published by
Wiley
ISBN 10:
1118486897
ISBN 13:
978-1-11848-689-4
Chapter 2 - Kinematics in One Dimension - Problems - Page 50: 46
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