A New (I think) Question About Squirt

[Williebetmore]

If the cue tip hits the CB on the same point, from the same angle and at the same speed, does changing only the cue stick's orientation with "swooping" backhand english change the amount of squirt?

View attachment 178698

I'm thinking that if the cue is angled toward the CB's center compared with the tip's direction of travel, then its effective endmass increases, creating more squirt. Anybody know?

pj
chgo

PJ,
These are totally different shots.

Use the Einstein construction for thought experiments. Seat an imaginary little man on the end of the cue tip, then imagine what he sees at contact (since contact is so brief in pool, it is a valid comparison). All the cue ball can "see" is location of impact and speed of hit - the cue is a straight piece of wood. You will see that location of impact is different on the 2 shots.

Backhand or "swooping" English is just a different way to go about applying spin - the end result depends only on speed and location of impact no matter how you go about achieving it.

The BHE'ers and "swoopers" think they get more because they are really just applying the tip further from center than they think they are because they are not looking directly at the cue ball along the line of the cue stick. The little imaginary man (can be clothed in green on St. Paddy's day in Chicago) sees the cue ball face on and is a great judge of location of impact.

 

[mikepage]

[...]
Now, the effect of the swoop stroke is still demonstrated by your 2nd diagram (albeit in exaggerated form). The cue is effectively moving forward at an angle. In this case, I agree with you that the amount of squirt would be larger as compared to the cue moving straight at the same effective tip offset. There would be more effective endmass because the cue will deliver more force along its axis (with a sideways component) and present more stiffness in the squirt direction. And with more squirt would come less spin (see TP B.7)![...]

A complication is that the usual squirt analysis is based upon conservation of sideways momentum: sideways momentum before the collision equals sideways momentum after the collision. In the usual case, the sideways momentum is always zero.

Here the "before" momentum is not zero. There's a small amount of system momentum to the right.

 

[Patrick Johnson]

PJ,
These are totally different shots.

I think the shots are functionally identical (except for the squirt difference) as long as the two tips are traveling in the same direction when they contact the CB (and hit the same spot at the same speed).

pj
chgo

 

[Williebetmore]

I think the shots are functionally identical (except for the squirt difference) as long as the two tips are traveling in the same direction when they contact the CB (and hit the same spot at the same speed).

pj
chgo

PJ,
Perhaps you meant to draw them differently (your "swooping" example hits closer to the center of the cue ball than your parallel example; no AutoCAD on AZB...). If the little man on the end of the cue sees the exact same location of impact; then the results will be the same (same squirt) unless some magical tip increases the contact time with the cue ball.

 

[dr_dave]

... Now, the effect of the swoop stroke is still demonstrated by your 2nd diagram (albeit in exaggerated form). The cue is effectively moving forward at an angle. In this case, I agree with you that the amount of squirt would be larger as compared to the cue moving straight at the same effective tip offset. There would be more effective endmass because the cue will deliver more force along its axis (with a sideways component) and present more stiffness in the squirt direction. And with more squirt would come less spin (see TP B.7)!...

A complication is that the usual squirt analysis is based upon conservation of sideways momentum: sideways momentum before the collision equals sideways momentum after the collision.

... not if you use the same reference frame as with the first shot, with the "sideways" direction still perpendicular to the total velocity of the cue tip.

Here the "before" momentum is not zero. There's a small amount of system momentum to the right.

Wow, you're really trying to impress the ladies now. :grin-square:

Regards,
Dave

 

[Patrick Johnson]

PJ,
Perhaps you meant to draw them differently (your "swooping" example hits closer to the center of the cue ball than your parallel example; no AutoCAD on AZB...). If the little man on the end of the cue sees the exact same location of impact; then the results will be the same (same squirt) unless some magical tip increases the contact time with the cue ball.

If viewed from the same direction (parallel with their direction of travel at the moment of contact, which is the same), then they hit the same CB contact point. Ignore the different cue angles when estimating this - that's the point.

pj
chgo