The general formula is:
[tex]y = y_{o} + v_{o}t - \frac{1*g*t^{2} }{2} [/tex] -- (A)
Where g = 9.8 m/s/s
[tex]v_{o}[/tex] = 0
[tex]y_{o}[/tex] = 100
a)
Time=t=3s.
Plug-in the values in (A)
y = 100 -(1/2*9.8*3*3)
y = 100-44.1 = 55.9m
Height of the ball exactly after 3 seconds = 55.9m.
b)
At ground, y=0; Plug-in values in (A):
A=> 0 = 100 - (1/2* 9.8 * [tex]t_{2}[/text])
Therefore t = + 4.52 s and - 4.52 seconds.
As t cannot be negative, therefore:
Time when ball hits the ground = 4.52s
-i
