Originally Posted by
soarbum
Velocity is a vector with components in x,y and z. ORAC clearly referred to zero vertical velocity, ie the z component. If it went up and came back down, then at some point, the vertical component was zero regardless of the shape of the trajectory.
I don't see why not if the object has a small enough cross section, a large enough mass and some fins to keep the pointy end at the front. Also bear in mind that the air density is much lower during the upper part of the trajectory.
ps: since you mentioned sky divers, low level divers reach 120mph while spread but Felix Baumgartner reached 843.6 mph (Mach 1.25) on his dive
Yes, he did. With decreasing altitude there is increasing air density, hence more drag. He slowed down at lower altitude. The comment I was responding to implied that every projectile on a ballistic path achieves some zero vertical speed then plummets to the ground with a final velocity depending on its maximum altitude. This is true for a vertical shot, but with any horizontal component there is a vector that does not go to zero at maximum altitude and carries a horizontal component that determines, with the altitude, the final velocity of the projectile. This is energy imparted to the projectile at launch and it does not vanish as the projectile achieves its maximum height, except for drag.