Tangent Line conundrum

Hickok

Hickok

Still shootin'
The initial direction of the cueball after contact is 90 degrees to the line taken by the object ball. Right?

I've been playing a long time and have learned (the hard way) to expect an angle closer to 86 degrees. Four degrees isn't much. But on stun shots with a pocket 3 or 4 diamonds away waiting to gobble the cue ball, four degrees becomes huge.

I was playing around recently with the VP simulator trying to figure out why 90 degrees doesn't work for me, and was surprised to find that it too shows a 'tangent line' of about 86 degrees.

Now, have I finally gone mad? Or is the 90 degree tangent line only a rough approximation offered to beginners?
 
...depends on cloth and weather conditions in addition to any minute english applied to the cue ball. Let's face it, conditions are less than ideal on any pool table and so physics and trigonometry apply less than ideally.
 
Remember that the tangent line is not 90 degrees from the point of contact. The path the cue ball will travel is parallel to the 90 degree from the point of contact but the cue ball will be moving along the line from where the cue ball is contacting the table. 90 degrees from the contact point would be the path that the edge of the cue ball would travel.
Steve
 
The direction the cue ball will travel after the hit depends on if the ball is sliding (stun) or rolling. The cue ball will come off the object ball in different directions depending on this!

And where the cue ball will go after that depends on if it is sliding, rolling forwards, rolling backwards, speed, etc. And where it goes after hitting a rail will depend on spin (english).

The best way to understand these basic principles and see them demonstrated is to get Dr. Dave's DVD. The book and articles on this did not get these through to my brain. The DVD did it because I could see him shooting the shots and explaining what was happening and why. Then I understood the diagrams and articles. I said to myself "Ah Ha!".

Get the DVD here...
http://www.engr.colostate.edu/~dga/pool/dvd_description.html
 
According to Physics the Cueball will always come of the objectball at a 90 degree angle. How long (far) the cueball stays on the 90 degrees is then a product of Speed & Spin.

On a very soft shot the cueball will diviate off the 90 degrees very quickly. The faster the cueball is traveling the harder it is to diviate off the tangent line....randyg
 
The CB initial tangent line for no side english shots will vary from close to 90 degrees on a thin cut to somewhere around 86 degrees on fuller hits. The reason for the loss of angle below 90 is friction.

Side english, will also produce small variations.

Of course, the CB resultant angle, after top or bottom english grips, will change considerably on fuller angle shots.
 
Hickok said:
Now, have I finally gone mad? Or is the 90 degree tangent line only a rough approximation offered to beginners?
Click to expand...

Beginners, first year physics students, ....

Funny things happens when friction is introduced.

Fred
 
I might further add that these rules are 30 degrees from the line of the hit and 90 degrees from the direction to the pocket (tangent)...
 
Billy_Bob said:
The direction the cue ball will travel after the hit depends on if the ball is sliding (stun) or rolling. The cue ball will come off the object ball in different directions depending on this!

And where the cue ball will go after that depends on if it is sliding, rolling forwards, rolling backwards, speed, etc. And where it goes after hitting a rail will depend on spin (english).

The best way to understand these basic principles and see them demonstrated is to get Dr. Dave's DVD. The book and articles on this did not get these through to my brain. The DVD did it because I could see him shooting the shots and explaining what was happening and why. Then I understood the diagrams and articles. I said to myself "Ah Ha!".

Get the DVD here...
http://www.engr.colostate.edu/~dga/pool/dvd_description.html
Click to expand...

I have to disagree. The cue ball ALWAYS leaves on a line 90° from the OB's path at the CB's point of release from the OB. How long it stays on that line, whether that is a short duration or long duration, depends on whether the CB is rolling, sliding, has backspin, overspin, etc., but it ALWAYS initially leaves on a 90° line from the OB path at the point of release, even though it may leave the tangent line "almost" immediately on a different path.

Now, there are three words in that statement that are VERY important. "Point of release". The CB and OB stay married, a condition called 'cling' for a period of time, depending on angle, speed, spin and other factors, like the weight of the CB. Weight of the CB is a huge factor. That is somewhat evident with CBs that are of slightly different weight... red Circle, blue dot, measles, etc., but is glaringly apparent with heavier magnetic CBs.

Later,
Bob
 
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Billy_Bob said:
I might further add that these rules are 30 degrees from the line of the hit and 90 degrees from the direction to the pocket (tangent)...

'splain this to me lucy...
Click to expand...

There's nothing to explain. One is on a stun shot and the other is on a naturally rolling (forward roll) ball, and the angles are measured from different things - the original angle of the cue ball (30 degree rule, natural roll) and the angle of the object ball (90 degree rule, stun).

What's to explain?

Cornerman said:
Beginners, first year physics students, ....
Funny things happens when friction is introduced.
Click to expand...

I think it's quite easy to explain the loss of four degrees due to throw. Throw would lessen the angle between the cue ball and the object ball's direction. Throw is caused by friction, and throw can be increased either due to standard throw or English throw.
 
Another Golden Rule of pool is to believe everything you see, expecially if there is an explanation that goes with it.
 
Wow! Very cool video clips. Imagine that our minds and strokes "feel" always adjust automatically to counter or minimize these effects. Nice to see a slow motion visual. Very cool....

.
.
 
Billy_Bob said:
Cue ball 90 degrees (stun)...
http://www.engr.colostate.edu/~dga/pool/normal_videos/NV3-4.htm
Click to expand...

If you look closely, you'll notice that again Dr. Dave cheated the video by trying to edit it, and that the deflection is less than 90°. On the first shot, you only have to watch the path of the object ball. It's not parallel to the triangle, but the cueball is parallel to its path. The object ball starts off an obvious distance from the triangle, but almost hits the triangle at the end.

That has been my big problem with many of these videos. They do actually show something, but the good Dr. doesn't realize what he's showing compared to what he's saying. The angle is slightly less than 90°.

Fred <~~~ can't wait to be accused of being a first class ass.
 
Cane said:
The cue ball ALWAYS leaves on a line 90° from the OB's path at the CB's point of release from the OB
Click to expand...

I'm sure this isn't true. I believe Bob Jewett just posted something on the follow shots that says that when the balls release, the cueball is not on the 90° (or even the 86°) path.

I think a lot of people who miss that stun carom/kiss shot will be happy to know that the angle is actually slightly less. They'll make more shots, and have more hair left on their head.

Fred
 
Cornerman said:
I'm sure this isn't true. I believe Bob Jewett just posted something on the follow shots that says that when the balls release, the cueball is not on the 90° (or even the 86°) path.

I think a lot of people who miss that stun carom/kiss shot will be happy to know that the angle is actually slightly less. They'll make more shots, and have more hair left on their head.

Fred
Click to expand...

I think the impressive part is just watching slow motion video. I think you will agree that there exists so many variables that the angle will vary from table to table, ball set to ball set and day to day. Clearly in a frictionless environment with only a perfect set of balls presents the only predictable outcome.

I believe what is important here is that there are effects to be noticed and billiard ball deflection angles are an approximation within a thin set of ranges.
 
Cornerman said:
Fred <~~~ can't wait to be accused of being a first class ass.
Click to expand...

Fred! You are a FIRST CLASS......


Just kidding...but didn't want you to be disappointed!;)
Steve
 
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