Legal trickshot, physically possible?

[frigopie]

Its not a double hit or foul...

1. Look at the cloth... it looks brand new so the cue ball is going to slide forward after a hard shot, no matter what you put on the ball..

2. Even on worn in cloth, the cue ball does not come straight back if you strike it hard...if its a little air-born, it can hop forward, or in this case, it slid forward before the friction grabbed it.

3. does not have to be a heavy ball to obtain this type of reaction..but makes it easier. #1 is the answer you are looking for.

I used to actually do this type of shot on really old cloth with no friction... You could shoot a ball straight in close to a pocket and follow it in the pocket (using draw) if you hit it hard enough.. Provided some really interesting shots and breakouts for 14.1

ummm I would like to see that...

 

[Mrdodd72]

With the speed he hit it, the cue ball slid too little to the side and curved forward too quickly. People who think it's not a double-hit please do the same shot with the cue ball and object ball 2 feet apart.





If you know elastic collision and conservation of momentum, then you know it's physically impossible for the cue ball (if it weighs the same as the object ball) to go forward (in any capacity) on a draw shot.

So are you saying the CB will never go forward of the contact point on a straight in shot when low English is applied? That might true the CB rebounded is soon as it contacted the OB, but there is always a fraction of a second where the CB remains in contact with OB. That is when English is transferred, and when "skid" happens. This is depends on conditions like cleanliness, humidity and speed. Most accomplished pool players understand and compensate for this. In this example he is shooting at an angle, this also effects the amount momentum transferred.
http://www.billiards.colostate.edu/high_speed_videos/HSV4-1.htm

 

[Patrick Johnson]

So are you saying the CB will never go forward of the contact point on a straight in shot when low English is applied? That might true the CB rebounded is soon as it contacted the OB, but there is always a fraction of a second where the CB remains in contact with OB. That is when English is transferred, and when "skid" happens. This is depends on conditions like cleanliness, humidity and speed. Most accomplished pool players understand and compensate for this.

It's easy enough to prove to yourself:

- use object ball for cue ball (same weight, marked)
- check chalk mark for center ball hit
- distance/speed for stun

If you actually do those things the CB won't penetrate the OB space appreciably.

pj
chgo

 

[Bob Jewett]

... but there is always a fraction of a second where the CB remains in contact with OB. ...

The cue ball moves forward into the object ball by less than a millimeter or two during contact. That is about the maximum forward penetration during contact you can expect on a draw shot when the cue ball is not off the table.

You can estimate the penetration yourself by measuring the contact patch between cue ball and object ball -- with carbon paper or wax or condensation -- and then doing the geometry to find the height of a spherical "cap" with that diameter on a pool ball. A contact patch 15mm across -- which larger than will normally occur between pool balls -- corresponds to a flattening of 1mm of each ball.

The time for the ball-ball collision is around 200 microseconds or 1/5000th of a second. This varies with speed and is shorter for higher speeds of shot.

 

[NervousNovice]

So are you saying the CB will never go forward of the contact point on a straight in shot when low English is applied?That might true the CB rebounded is soon as it contacted the OB, but there is always a fraction of a second where the CB remains in contact with OB. That is when English is transferred, and when "skid" happens. This is depends on conditions like cleanliness, humidity and speed. Most accomplished pool players understand and compensate for this. In this example he is shooting at an angle, this also effects the amount momentum transferred.
http://www.billiards.colostate.edu/high_speed_videos/HSV4-1.htm

The real world situation is not perfectly perfectly elastic, and collision and the transfer of energy don't occur instantaneously. So strictly speaking, it does go forward a tiny bit, but not in an easily observable way, and definitely not to the extend that the cue ball would follow the object ball into the pocket.

 

[Bob Jewett]

The real world situation is not perfectly perfectly elastic, and collision and the transfer of energy don't occur instantaneously. So strictly speaking, it does go forward a tiny bit, but not in an easily observable way, and definitely not to the extent that the cue ball would follow the object ball into the pocket.

Especially if there is serious draw on the cue ball.

 

[4onthebreak]

Foul

Look at the finial stroke at :13. The cue finishes past both balls. Do the balls have time to move before the cue would end there? No. So, how can it come to rest there on a full power stroke? It pushed the balls out of its way.

 

[deanoc]

Those shots require a stroke and english

 

[Patrick Johnson]

Look at the finial stroke at :13. The cue finishes past both balls. Do the balls have time to move before the cue would end there?

Yes.

EDIT: I looked at a frame-by-frame of the video and can't really tell. It's real close.

pj
chgo

 

[iusedtoberich]

I'm a bit rusty on my physics, but if you shot this shot on the bare slate without cloth, and with silicone applied to both balls, the CB would not go forward like it did. It would go on the tangent line.

Its the mass of the two colliding balls that determines their initial direction, not any friction. Then, any spin can take affect.

 

[Patrick Johnson]

I'm a bit rusty on my physics, but if you shot this shot on the bare slate without cloth, and with silicone applied to both balls, the CB would not go forward like it did. It would go on the tangent line.

Its the mass of the two colliding balls that determines their initial direction, not any friction. Then, any spin can take affect.

Agreed - unless it's a double hit.

EDIT: ...or a heavy CB.



pj
chgo

 

[Bob Jewett]

Agreed - unless it's a double hit.

pj
chgo

Well, yes, but it could also be a heavy cue ball. Hard to tell on that video.

 

[Patrick Johnson]

Well, yes, but it could also be a heavy cue ball. Hard to tell on that video.

Yes, I forgot to include that possibility (fixed in my post).

pj
chgo

 

[Wybrook]

Can you show us a video of you doing the same shot with equal-weight balls and not fouling?

Sure.. I'd love to. As soon as my room changes the cloth, I will take a video with some Super Aramith Pro Cup on Simonis 860..

There are several trick shots like this that only work on really new cloth or really old cloth.. I can do variations of this, but they don't arc as nice unless the cloth is slick..

And yes, the balls will slide forward if you hit it straight on with draw, but only under particular circumstances.. I have done it on super old cloth that played like glass.. If you hit the balls hard enough, a little below center, it will slide forward then as the spin grabs, come shooting back..

If you don't know what I'm talking about then maybe you just never played in these conditions.. I understand the physics behind normal conditions, but there are extremes. (fun to play with too!!)

You know this stuff.. C'mon Bob...

(its bottom right and hit a smidge off-center) pretty basic really.

 

[frigopie]

Sure.. I'd love to. As soon as my room changes the cloth, I will take a video with some Super Aramith Pro Cup on Simonis 860..

There are several trick shots like this that only work on really new cloth or really old cloth.. I can do variations of this, but they don't arc as nice unless the cloth is slick..

And yes, the balls will slide forward if you hit it straight on with draw, but only under particular circumstances.. I have done it on super old cloth that played like glass.. If you hit the balls hard enough, a little below center, it will slide forward then as the spin grabs, come shooting back..

If you don't know what I'm talking about then maybe you just never played in these conditions.. I understand the physics behind normal conditions, but there are extremes. (fun to play with too!!)

You know this stuff.. C'mon Bob...

(its bottom right and hit a smidge off-center) pretty basic really.

You better weigh the CB and OB before making the shot ...

 

[Bob Jewett]

... You know this stuff.. C'mon Bob... ..

Maybe. That's why I asked for a video.

 

[Wybrook]

You better weigh the CB and OB before making the shot ...

haha.. I will video me weighing the cue ball and object ball, then go directly to the shot setup without cuts..

I can't believe this shot is causing any kind of questioning...
Has no one played on new cloth before?

 

[Patrick Johnson]

... I will video me weighing the cue ball and object ball

Use a striped object ball as the cue ball, with the stripe horizontal so we can see where you hit it (show us the chalk mark).

Has no one played on new cloth before?

You must be the only one...

pj
chgo

 

[iusedtoberich]

I sent a friend request to the FB user who made this shot. If he responds, I will ask him to come join this discussion.

In the meantime, it looks like the CB did not touch the rail, according to the shooter. See his comment below. I don't think that changes our discussion here that much, but its just more information.

This shot looks like a fouette shot, with either non-standard balls, a double hit, or a magic shooter

 

[iusedtoberich]

I just tried the shot myself, and made it on the first try! (Lucky, I promise)

Notice, my CB went forward maybe 1/4 ball diameter. I think this was actually due to the camera perspective and slight cut angle. I hit it with slight low right.

You can put the video to play on slow motion speed on the youtube settings. And I have the original recording that is 24 frames per second, and I can show further frames if anyone wants to see them (I think I can anyway...)


https://youtu.be/TPqeRt-7oXY