Answer:
Step-by-step explanation:
Vertical POSITION will be found by
Ut - 1/2 a t^2 where a = 9.81 m/s^2
the SECOND particle position will be
U(s+t) - 1/2 a ( s+t)^2
equate them to find when they are at the same position
Us - 1/2 as^2 = Us + Ut - 1/2 a ( s^2 + 2st + t^2 )
0 = Ut - 1/2 a ( 2st+ t^2 )
0 = Ut - ast - 1/2 a t^2