initial velocity, u = 0
distance dropped be h
if h = 4.9 m
we know acceleration, g = 9.8 m/s.s
thus using second equation of motion, h = ut + 1/2gt2
we can find time required t.
for that t, we can use first equation of motion to find final velocity, v
v = u + gt
for last part, the acceleartion remains same, only velocity varies.