Physics help?

Question

A ball is thrown straight up with an initial
speed of 70 m/s.
How high does it go? Assume the accelera-
tion of gravity is 10 m/s2 : Answer in units of
m.

How long is it in the air? Answer in units of
s.

Answer 1

Actually g is still 9.81m/s^2

h=V0t -0.5gt^2

V0=gt=70m/s
so t=V0/g

h= (V0)^2 / g - 0.5 g (V0/g)^2
h=(V0)^2 / g - 0.5 V0^2 / g=0.5 V0^2 / g

a) h=0.5(70)^2 /9.81=250m
b)t(total)=2t=2V0/g=2x70/9.81=14.3 s