These arrows will decrease their speed by the gravity according the following rule:
Vf = Vi - g*t, where Vf is final speed, Vi initial speed, g is gravity constant and equal to 9.8 m/s2 and t is time elapsed.
Then for the first arrow we can calculate the time to reach the màximum height, which is the point where final speed is equal to zero, so:
0=31.8 - 9.8*t => t=31.8/9.8=3.24 seconds
Now we also know that both arrows reach maximum heights at same time, so for the second arrow we need to substrat the delay between both shots, the time till arrives at top position is in 3.24-1.82 = 1.42 seconds
So then, inital speed of the second arrow is:
0=Vi-9.8*1.42 => Vi=13.96 m/s
