Why the Newton's second law of motion important?

Newton's Second Law of Motion F=ma is very important because it shows the relationship between forces and motion. It allows you to calculate the acceleration (and therefore velocity and position) of an object with known forces.

This is incredibly valuable for scientists, engineers, inventors, etc. By controlling, measuring, or calculating the force exerted on objects, we can map out their trajectory, thus knowing where they will be at any given time.