The horizontal and vertical components of two-dimensional motion are:

1. This is the single most useful fact in projectile motion. 2. The independence of motion states that the horizontal and vertical components of two-dimensional motion are independent of each other. 3. So what happens vertically does not change what happens horizontally. 4. That independence is exactly what makes resolving the motion worthwhile. _Source: OpenStax College Physics for AP(R) Courses 2e (CC BY 4.0), Ch 3 'Two-Dimensional Kinematics', sections 3.1-3.4_