physics
posted by Nick .
Two diamonds begin a free fall from rest from the same height 0.9 s apart. How long after the first object begins to fall will the two objects be 11 m apart?

Let t=0 be the time the first one is dropped. The distance that it falls after that is
y1 = (g/2)t^2 = 4.9 t^2
The distance that the second one has fallen at time t(>0.9s) is
y2 = (g/2)(t0.9)^2 = 4.9(t0.9)^2
You want to solve for the time t when
y1  y2 = 4.9 [t^2  (t1)^2] = 11 m
2t  1 = 11/4.9 = 2.24 s
t = 1.62 s 
Two diamonds begin a free fall from rest from the same height 1.2 s apart. How long after the first object begins to fall will the two objects be 20 m apart?