Answer:
The  value is  [tex]v =  12.5 \  m/s[/tex]
Explanation:
From the question we are told that
  The  height is  [tex]h  =  50 \  m[/tex]
  The  time taken is  [tex]t =  8 \ s [/tex]
 Â
From the equation of motion we have  that
 [tex]s =  ut + \frac{1}{2}  * a * t^2[/tex]
Here u = 0 Â because the rocket started at rest
 [tex]50 =  0 + \frac{1}{2} * a  * 8^2[/tex]
=> Â [tex]a = Â \frac{100}{64}[/tex]
=> Â Â [tex]a = Â 1.5625 \ m/s^2[/tex]
Also from the kinematic equation we have that
  [tex]v  =  u + at[/tex]
=> Â [tex]v = Â 0 + Â (8 Â * Â 1.5625)[/tex]
=> Â [tex]v = Â 12.5 \ Â m/s[/tex]
   Â