Acceleration question?

Question

Falling objects drop with an average acceleration of 9.8m/sec/sec or 9.8m/sec to second. If an object falls from a tall building, how long will it take before it reaches a speed of 49m/sec? How is that calculated?

Answer 1

v=at
v=49m/s
a=-9.8m/s (pay attention to the negative not neccessarly for this problem, but ones you will do later!)

therefore:
v/a=t
(49m/s) / (-9.8m/s)= -5s well you can't have a negative time, therefore t=5s

Answer 2

v = at (starting from rest)
49 m/s = (9.8 m/s²)t
t = 49 / 9.8 seconds

(neglecting effects of air, of course)