The initial speed of the boy's thrown is determined as 16.03 m/s.
The initial speed of the throw is calculated as follows;
h = vt - ¹/₂gt²
4 = 3t - (0.5)(9.8)(3)²
4 = 3t - 44.1
3t = 48.1
t = 48.1/3
t = 16.03 m/s
Thus, the initial speed of the boy's thrown is determined as 16.03 m/s.
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