as we know that
acceleration = 0.50 m/s^2
distance traveled = 125 m
time taken = 20 s
now we will use the equation of kinematics
[tex]d = v_i*t + \frac{1}{2}at^2[/tex]
[tex]125 = v_i* 20 + \frac{1}{2}*0.50*20^2[/tex]
[tex]125 = 20*v_i + 100[/tex]
[tex]125 - 100 = 20*v_i[/tex]
[tex]v_i = 1.25 m/s[/tex]
so its initial speed must be 1.25 m/s