First, we need to calculate the amount of time that the balls are falling, using the formula:
![\Delta S=(gt^2)/(2)](https://img.qammunity.org/2023/formulas/mathematics/college/y7b503pq8fbbwcn7yebla9xa7whwceu5gf.png)
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:
![\begin{gathered} 125=(10t^2)/(2) \\ 125=5t^2 \\ t^2=25 \\ t=5\text{ s} \end{gathered}](https://img.qammunity.org/2023/formulas/physics/college/rkkh37e8jwfve3ozcn875ohkll6m13d3hy.png)
Now, to find the initial speed v, we can use the formula for the distance traveled in the horizontal movement:
![\Delta S=V\cdot t](https://img.qammunity.org/2023/formulas/physics/college/bj77kwqmkjrjb4cqv091mv45zegmc1x2dp.png)
For DeltaS = 30 and t = 5, we have:
![\begin{gathered} 30=V\cdot5 \\ V=(30)/(5) \\ V=6\text{ m/s} \end{gathered}](https://img.qammunity.org/2023/formulas/physics/college/rhllzni0rl0eivheux9yu2v6njgwowvcak.png)
So the initial speed v is 6 m/s.