People keep saying this is a foul based on where the cue ball went, which I understand. But I am also curious where the cue ball would go if it is a simultaneous hit and there was spin on the cue ball, and if simultaneous hits are considered legal by these rules.
Sharivari has a good video discussing the shot and showing 8-first and 4-first shots. In each case the cue ball follows the ball it hit second. That is for shots that clearly hit one ball first.
A very general principle in physics says that as the incoming line of cue ball is very gradually changed from hitting one ball first to the other ball first, the final path of the cue ball will smoothly vary from one direction to the other. These in-between directions happen when the cue ball is in contact with the two balls simultaneously. The contacts are not instantaneous. They last about 0.2 milliseconds or 200 microseconds, or about a tenth as long as tip-ball contacts.
The "normal" situation is that the contact begins with one of the object balls, the cue ball and first object ball acquire their new speeds and directions, and then the cue ball leaves contact with the first ball. It travels a little distance and then contacts the second ball.
The unusual situation is when the cue ball is still in contact with the first ball when it hits the second. The two contacts overlap in time. This is pretty rare, because the duration of each contact is so short.
A reasonable way to decide which was first for overlapping contacts is to see which of the "normal" paths the cue ball is closer to. This requires you to know what the normal paths are. A very simple case is when shooting directly between two frozen object balls. If the cue ball comes perfectly straight back, you hit the balls simultaneously. If it goes even slightly to either side, that tells you which was struck first. I have seen the cue ball come back within a couple of degrees of straight back, but never perfectly straight back.
I think the positions of the balls for the shot in question was pretty complicated and it was not easy to predict the exact paths of the cue ball for various sequences of hit. Maybe a video review would have helped, but I doubt that the actual collisions would have been in separate frames. The frames are typically around 10 milliseconds apart and only very expensive equipment could see the actual ball-ball contacts.
www.wst.tv
Keep Peterson busy bump.
