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Why Does This Work?
© Copyright 2002, Jim Loy
We want to shoot the red ball into the corner pocket by kicking at
it, three rails (hitting three rails then the red ball). The obvious way is to
shoot a natural, top rail (in the diagram), left end rail, bottom rail, bingo
(see Three Rail Kicks and Banks). But on some tables,
there is an even easier shot, which I have drawn in the diagram. Shoot
moderately hard to the closest end rail with maximum reverse English (right
English in the diagram). On some tables, it is nearly impossible to miss. This
is my trick shot.
Why? Why does this work? In the diagram, we have right English, which
slides on the first rail. The right English grabs on the second rail, making
the cue ball go almost straight across to the opposite long rail. But here, the
cue ball mysteriously has left English, and goes back toward the first end
rail. Why? What happened to the right English?
OK, you may argue that right English is really left English on the
opposite rail? No, of course not. Right English is counter-clockwise spin, no
matter which direction the ball is moving. If the ball changes direction,
counter-clockwise spin is still counter-clockwise spin. You can walk all around
the cue ball as it spins counter-clockwise, and from any angle, it is always
spinning counter-clockwise. On some tables, mostly with slick cloth, if you
shoot the above trick shot, when the cue ball hits the third rail, it will
still have right English, and (when it hits the third rail) will bounce out
away from the right end rail, missing the trick shot. So, depending on the
table, we end up with totally opposite spins from the same exact shot.
So, why does my trick shot work on some tables? The trick is the second
rail. The cue ball grabs on that rail, and the rail gives the opposite spin to
the ball. It is the effect that we see with a Super
Ball. Put right English on the Superball as you drop it to the floor, and
it bounces back up with left English. When it hits the floor again, it reverses
English and again has right English. That is why a Super Ball changes direction
on every bounce, the spin keeps changing. Actually, while the Super Ball is in
contact with the floor, the floor grabs the ball, and the ball deforms
sideways. And as the deformation snaps back to its original nondeformed shape,
it torques the ball in the opposite direction. In our pool shot, the rail
deforms instead of the ball, and snapping back to its nondeformed shape torques
the ball in the opposite direction. But if the cloth is slick, then the rail
does not grab the ball, and the spin does not reverse.
This is just one of the many complications that makes billiards so
interesting. And it is one of the reasons that reverse English is so
unpredictable. Will it slide? Will it grab?
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