[MJT]

Originally posted by Bob M.
REPLY: Since we're talking physics, I thought I might chime in.

A pass thrown on a football field has three orthogonal (perpendicular) component vectors: One (call it X) is parallel to the surface of the field and to the sideline plane, in other words straight up and down the field; another (call it Y) parallel to the surface of the field but perpedicular to the sideline plane, in other words back and forth across the field; and a third (call it Z) perdendicular to the surface of the field, in other words straight up. Likewise, a runner moving on a football field moves in a manner that can be resolved into two component orthogonals--like X and Y above. For simplicity, we can ignore the insignificant Z component of a player's movement since he's incapable of flight! The velocities (directed vectors) of the runner in motion and the ball can be resolved into their component parts, each with it's own magnitude (speed, in this case).

The problem being analyzed is a simple matter of vector arithmetic. And the only consideration needed to rule properly for NCAA is the arithmetic sum of the X components of the ball in flight and runner's motion. For simplicity's (yeah, right!) sake, let's orient ourselves so that downfield is positive and upfield is negative. Also, let's call the upfield-downfield component of the runner Xr and call the same component of the pass in flight Xp. If Xp + Xr > 0, the ball will land downfield from the point of origin (the point where the pass was released) and the result will be an illegal forward pass.

For Federation, since the only requirement is that the initial direction of the pass not be forward, all we are concerned with is the initial velocity of the ball in the X direction, i.e. Xp. As long as Xp <= 0, then the pass is legal. The velocity of the player in the X direction is not material to the Fed's requirements.

Now all of this ignores any possible wind that might be present. If there is a wind present, it's orthogonal components must also be resolved and consolidated into the resultant velocity. And again, the only component we're interested in is the X component of the wind, Xw. Therefore, in order to have a legal forward pass in NCAA when there's a wind blowing, the mathematical requirement would be that Xp + Xr + Xw <= 0. And the effect of the wind in Federation is not a concern since the only requirement for a legal forward pass in Federation is Xp <=0.

MJT...am I right?

I understand, and agree! It is totally different in NCAA and NF. In NF, there is only ONE factor to consider, initial direction, while in NCAA it is simply based on the end result.