Seems this is difficult for beginners to understand...
That is when you have ball in hand, if you shoot in the object ball at an angle, you have many options as to where the cue ball will go after the shot as well as what you can get the cue ball to do for you after it contacts the object ball.
When you align the cue ball for a straight in shot to the pocket, you basically have the options of follow, stop, or draw (cue ball stays in line with your shot).
BUT when you shoot in the object ball at an angle, you can do nifty things. Like accomplish two things with one shot such as making your ball, and with the same shot, breaking out a troublesome cluster. Or leaving the cue ball where you need it for your next shot.
Using the 30 and 90 degree rules along with an angled shot, you can see that if you hit in a certain ball at a particular angle and use follow or stun as appropriate, you can get that cue ball to head right toward that nasty cluster and break it up after your shot!
And when keeping in mind that "What goes forward will hit the rail and come back!", you can use follow, shoot in your ball at a certain angle, then the cue ball will roll forward after your shot, hit the rail, then roll back to where you need it for your next shot.
I've been trying to communicate this to a friend of mine. I pointed this out over and over and over. He would get ball in hand, then set it up for a straight in shot everytime. Well he finally saw the light... He got ball in hand and set it up at an angle to leave the cue ball where he wanted for his next shot. It worked. I have not seen him set up a straight in ball in hand shot since... "Hummm... on to a good thing here!"
30 degree rule (Use follow - hit cue ball above center)...
http://www.engr.colostate.edu/~dga/pool/normal_videos/NV3-9.htm
90 degree rule (Stun shot - cue ball is sliding, not rolling)...
http://www.engr.colostate.edu/~dga/pool/normal_videos/NV3-4.htm
That is when you have ball in hand, if you shoot in the object ball at an angle, you have many options as to where the cue ball will go after the shot as well as what you can get the cue ball to do for you after it contacts the object ball.
When you align the cue ball for a straight in shot to the pocket, you basically have the options of follow, stop, or draw (cue ball stays in line with your shot).
BUT when you shoot in the object ball at an angle, you can do nifty things. Like accomplish two things with one shot such as making your ball, and with the same shot, breaking out a troublesome cluster. Or leaving the cue ball where you need it for your next shot.
Using the 30 and 90 degree rules along with an angled shot, you can see that if you hit in a certain ball at a particular angle and use follow or stun as appropriate, you can get that cue ball to head right toward that nasty cluster and break it up after your shot!
And when keeping in mind that "What goes forward will hit the rail and come back!", you can use follow, shoot in your ball at a certain angle, then the cue ball will roll forward after your shot, hit the rail, then roll back to where you need it for your next shot.
I've been trying to communicate this to a friend of mine. I pointed this out over and over and over. He would get ball in hand, then set it up for a straight in shot everytime. Well he finally saw the light... He got ball in hand and set it up at an angle to leave the cue ball where he wanted for his next shot. It worked. I have not seen him set up a straight in ball in hand shot since... "Hummm... on to a good thing here!"
30 degree rule (Use follow - hit cue ball above center)...
http://www.engr.colostate.edu/~dga/pool/normal_videos/NV3-9.htm
90 degree rule (Stun shot - cue ball is sliding, not rolling)...
http://www.engr.colostate.edu/~dga/pool/normal_videos/NV3-4.htm