This is one that annoys me. I think its exaggerated how far the ball would go forward just on the momentum of the moving player
No it isn't
Its an immeasurable factor
No it isn't, but it actually doesn't need to be measured, because the ball has the momentum of the player who is carrying it.
If that player, especially a back, is running at, say a 100m in 15 seconds pace (not unreasonable) then the player is running at over six and a half metres per second (6.7 m/s to be precise) and that means the ball MUST also have that momentum since the player is holding it. These are FACTS; not the Laws of Rugby, the Laws of Physics; simple, 8th Grade (Year 13) school physics.
This means the player passing the ball, just to throw the directly backwards to a player behind him, must throw the ball backwards at over 6.7 m/s to cancel that momentum. If you think that is hard, then wait, there's more; it gets harder, the wider the pass is either side of straight behind,
A pass at 45° has to be thrown at 9.5 m/s (35 km/h).
A flatter pass at, say 22.5° behind level with the passer, has to be thrown at 17.5 m/s (63 km/hr)
Reduce that to what would a reasonable pass angle of 10° and the speed of the pass required to cancel ball carrier's momentum is 38.6 m/s (139 km/h).
A flat pass of 1° behind level has to be thrown at literally supersonic speed; 384 m/s (1380 km/hr)
and I would be much happier if they ignored any potential momentum and only allowed passes that actually went backwards.in relation to the pitch. I've seen some commentators try to use the position of the passer,in relation to the ball, when caught , as proof of backward/forward pass, but this doesn't take into account the backward momentum the passer has applied to the ball.
It would simplify things if they totally ignored momentum.
No you would not be happy at all, because the game would be unplayable at anything beyond walking pace.