Answer
$v_{f}=42m/s$
Work Step by Step
We know the following equation:
$v^{2}_{f}=v^{2}_{0}+2gx$
We plug in the known values to obtain:
$v_{f}=\sqrt {v^{2}_{0}+2gx}=\sqrt {(0m/s)^{2}+2(9.8m/s^{2})(90m)}=42m/s$
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