Answer:
v = 3.65 m / s
Explanation:
In this exercise we use the conservation of mechanical energy
starting point. Point A compressed spring
     Em₀ = 100 J
final point. Point B uncompressed spring
     Em_f = K = ½ m v²
energy is conserved
     Em₀ = Em₀_f
     100 = ½ m v²
     v = [tex]\sqrt{ \frac{2 \ 100 }{m} }[/tex]
     v = [tex]\sqrt {200/15}[/tex]
    Â
     v = 3.65 m / s