Answer:
(A)
Set the initial height equal to gt2/2 and solve for t.
h0 = gt2/2
t = √(2h0/g)
h0 = 169.2 m
g = 9.8 m/s2
Plug in the numbers and get t in seconds.
(B)
x = vxt
vx = 5 m/s
t = result from part (A) in seconds
Plug in the numbers and get x in meters.