Reverse plants with balls not touching - please explain

[legod]

Ok - I've been playing snooker a number of years but I can't get my head around the science of the reverse plant - at least not without a well-presented scientific answer to satisfy my curious mind.

I've always known about the reverse plant in the situation where the red balls are touching. It's very useful to know the reverse plant effect in order to 'make' plants that aren't on. On the whole, I'm pretty good at judging plants. At least I thought I was until a game last night I spent 30 seconds sizing up what I thought was the correct angle to hit Red 1 (which was about half a little finger's width away from Red2) in order to pot Red 2, only to gasp in horror when the red went the 'wrong' way.

As my understanding goes, if the balls are touching, the first red will have a 'push' effect on the 2nd red.

The same phenomenon occurs also when the reds are very close together without touching....except I can't quite see why. If I was using Red 1 as a cue ball to pot Red 2, it wouldn't be sending Red 2 in the same direction as if I was playing the reverse plant, would it?

My question is how does that work? It seems to defy logic. I'd like to see some sort of slo-mo replay of this sort of reverse plant in action. Anyone got a scientific explanation for it?

Also - what is the maximum distance between red balls that this 'reverse plant' phenomenon can occur? (there must be some physics geek with an equation to work this out).

Thanks

[Krypton]

The ball contact is not infinitesimally short.

imagine 2 reds touching: hit the first on the left side will result in the rear one drifting off to the right. that is logical to you, I think:

cueball hits first red, on the left, and pushes the whole mass of two reds to the right.

the same applies if the reds are NOT touching, but very close: cueball hits first, stays in contact for a fraction of time, whilst the second red is also hit and becomes part of the three ball pack - with the result of it being pushed to the right.

Once you got that, you can find the solution to you last question: WHEN is 'slightly apart' 'too far apart' to aim as if they were touching: this can only be answered for a certain cueball speed. the faster the shot, the 'longer' the contact (due to deformation of the balls and similar effects), the wider the balls may be apart and still behave as if they were touching. on slow shots then, 5 mm i.e. is enough of distance to aim like if they were far apart, on a very hard power stroke, the shot might not even be on or has to be aimed differently.

experience will tell you. go and experiment with various ball setups.