A spring of natural length $l$ and spring constant $50\, N/m$ is kept on a horizontal frictionless table with one end attached to a rigid support. First the spring was compressed by $10\, cm$ and then released to hit a ball of mass $20\, g$ kept at a distance l from the rigid support. if after hitting the ball, the natural length of the spring is restored, what is the speed with which the ball moved? (Ignore the air resistance)