Interference, Obstruction or Train Wreck??

[tibear]

Had a discussion with a friend the other day about the following:

Situation 1: R1, less then two out. Batter hits a ground ball back up the middle, hits the pitcher and is rolling towards F4. R1 is running towards second and there is a collision with F4 as he is coming in to play the ball. What's the call?

Sit 2:Would it make any difference if F4 isn't running but standing still when R1 and F4?

Sit 3:Would it make any difference if the ball never touches the ground when R1 and F4 collide? i.e. Ball is hit and then deflected by F1 towards F4?

My inclination is:
Sit 1: Obstruction
Sit 2: Interference because I would assume R1 intentionally hit F4.
Sit 3: Interference on R1.

Depending on the play I might call a double play on the interference calls.