Given data:
The value of the spring constant is,
[tex]k=180Nm^{-1}[/tex]
The value of the mass of the cart is,
[tex]m=3.2\text{ kg}[/tex]
The distance moved by the cart from the equilibrium is,
[tex]\begin{gathered} d=40\text{ cm} \\ d=0.4\text{ m} \end{gathered}[/tex]
The acceleration acquired by the cart is,
[tex]\begin{gathered} kd=ma \\ 180\times0.4=3.2\times a \\ 72=3.2\times a \\ a=22.5ms^{-1} \end{gathered}[/tex]
The initial velocity of the cart is,
[tex]u=0ms^{-1}[/tex]
The velocity of the cart when it passes the equilibrium is,
[tex]\begin{gathered} v=u+2ad \\ v=0+2\times22.5\times0.4 \\ v=18ms^{-1} \end{gathered}[/tex]
Thus, the velocity of the cart is 18 meter per second.