Can you please explain how use the force model to answer the question A 2kg block is initially moving at 4 m/s to the right on a frictionless,

Can you please explain how use the force model to answer the question "A 2kg block is initially moving at 4 m/s to the right on a frictionless, level surface when a 5N force is applied straight down, while the block displaces by 1.6 m. What is the blocks final speed?" I also need to know how to apply the work-kinetic energy theorem to answer this question. I need some physics help, and I would really appreciate it!