A 20 kg block moving along a frictionless horizontal surface is connected to one end of a horizontal spring (k = 500 N/m), the other end of which is stationary. When the block passes the equilibrium position (the point where the force of the spring is 0), the kinetic energy is 20 J. The moment the piece passes the equilibrium position and the spring is compressed by 0.20 m, what is the speed of the piece?