This article will explain in more detail the state of the cue ball as it travels towards the object ball that makes the cue ball stop at the moment it impacts the object ball.
Refer to Figure 1 below. At the moment the cue ball impacts the object ball, the cue ball does not contain any spin on it, ie. no backspin or forward spin. At this state, right before impact, the cue ball simply “slides” through the cloth. I shall refer to this as “Slide” as illustrated in the graphic below.
On shots where the object ball is close to the cue ball, all you need to do in order to execute a Stop Shot is to “slide” the cue ball towards the object ball. This can be done with a center ball hit on the cue ball. However, on longer shots you cannot just slide the cue ball towards the object ball. As discussed previously, friction takes effect at a certain distance that the cue ball travels, therefore, as friction takes effect, the cue ball that was previously just sliding through the cloth will now generate forward spin. To counter this effect, you will need to to apply backspin on the cue ball so that as friction takes its effect, the backspin will simply be converted into “slide”. Refer to the example above. Let’s say you have a long distance between object and cue ball. You will hit the cue ball with below center stroke creating backspin. At a certain distance, the friction on the cloth takes effect and removes the backspin on the cue ball. At this point, the cue ball no longer has spin and it is a this moment that it should contact the object ball which will result in a Stop Shot.
Now, there’s still the question of when you should hit the cue ball with a center ball hit and when you should use a below center hit. How low should I hit the cue ball? How much spin should I put on the cue ball? How much speed? These questions can only be answered through practice. You now have all the knowledge to explain how the stop shot works, the next step is to apply this knowledge at the table.