First, we need to calculate the amount of time that the balls are falling, using the formula:
[tex]\Delta S=\frac{gt^2}{2}[/tex]Where DeltaS is the distance traveled, g is the gravity acceleration and t is the time.
So, for DeltaS = 125 and g = 10, we have:
[tex]\begin{gathered} 125=\frac{10t^2}{2} \\ 125=5t^2 \\ t^2=25 \\ t=5\text{ s} \end{gathered}[/tex]Now, to find the initial speed v, we can use the formula for the distance traveled in the horizontal movement:
[tex]\Delta S=V\cdot t[/tex]For DeltaS = 30 and t = 5, we have:
[tex]\begin{gathered} 30=V\cdot5 \\ V=\frac{30}{5} \\ V=6\text{ m/s} \end{gathered}[/tex]So the initial speed v is 6 m/s.