Answer
(a) $58~m/s$
(b) $5.9~s$
Work Step by Step
(a) We know that
$v_i=\sqrt{2gh}$
We plug in the known values to obtain:
$v_i=\sqrt{2(9.81m/s^2)(170.7m)}$
$v_i=58m/s$
(b) We know that
$t=\frac{2h}{v_i+v_f}$
We plug in the known values to obtain:
$t=\frac{2(170.7m)}{58m/s+0m/s}$
$t=5.9s$
