Components of Projectile Motion (1 Viewer)

[phoenix159]

What is the mathematical significance of the vertical and horizontal motions being perpendicular?

 

[treebrains]

Because gravitational force only acts downward (i.e. perpendicular to surface of Earth) then it is only a factor to be considered in vertical motion. i.e.: (v)y = (u)y + a(t) -> you know (if on Earth) a=-9.8 of course, so (v)y = (u)y - 9.8(t) automatically.
It also makes horizontal analysis much simpler because there is no grav force acting horizontally on the surface of earth, hence a=0.
(v)x = (u)x + a(t) -> you know a = 0, (v)x = (u)x
this applies to the other equations of motion. You just take a=0 for horizontal motion.