As you learned in the previous lesson, a stop shot can be made when the cue ball has no forward or backwards spin on impact with the object ball. This means that if the two balls are lined up in a totally straight line when they hit, there should be no movement from the cueball. This makes for a predictable outcome when trying to set yourself up for your next shot. Unfortunately, not every shot will be straight in, so how do we know where the cue ball will end up if we apply a stop shot with two balls that aren't perfectly aligned?
Fortunately, there is a system to figure this out as well. When the cue ball has no spin when it hits the object ball the angle it comes off will be 90 degrees perpendicular to the tangent line.
A great way to visualize this when you are playing in a game of pool is to utilize Dr Daves suggestion of using your hand as a guide. Simpy make an L shape with you thumb and forefinger. Point your indexfinger along the line you want the object ball to go and keep your thumb at a 90 degree angle with the L shape still intact. Wherever your thumb is pointing to is where the cue ball will end up after contact.