physicists: tip:ball contact time

Ballistic Billiards

Ballistic Billiards

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The general consensus seems to be that the dwell time of the tip
on the ball is ~1ms (millisecond) or 1/1000 of a second.

This is interesting to me because, in golf, the dwell time is considerably
shorter at ~.5 ms. Yet in that ~.5 ms, while the club is in contact with
the ball, the club has moved the whole way through the ball.

Even in tennis, with a soft ball, the contact time is only ~5 ms.
Croquet, ~1 ms.
In croquet, tests have been done that show a variance in the
contact time upwards of 2ms.
The numbers that I saw were 1.5-3.7 ms. depending upon what type
of stroke was used.

Back to billiards.
Without doing the math, it seems that the tip is in contact with
the ball for the first few inches of the CB:OB journey.
Maybe someone wants to do the math, I don't.

Here's one link with some reference and interesting points about
the physics of croquet vs golf. Link
I'll add another one later.
 
coopdeville said:
The general consensus seems to be that the dwell time of the tip
on the ball is ~1ms (millisecond) or 1/1000 of a second.

This is interesting to me because, in golf, the dwell time is considerably
shorter at ~.5 ms. Yet in that ~.5 ms, while the club is in contact with
the ball, the club has moved the whole way through the ball.

Even in tennis, with a soft ball, the contact time is only ~5 ms.

5X longer than a pool shot seems right to me.

Croquet, ~1 ms.
In croquet, tests have been done that show a variance in the
contact time upwards of 2ms.
The numbers that I saw were 1.5-3.7 ms. depending upon what type
of stroke was used.

Back to billiards.
Without doing the math, it seems that the tip is in contact with
the ball for the first few inches of the CB:OB journey.Maybe someone wants to do the math, I don't.

Here's one link with some reference and interesting points about
the physics of croquet vs golf. Link
I'll add another one later.
Click to expand...

Slow mo video shows that not to be true. Unlike golf, the pool cue slows down dramatically at CB contact so there is a dramatic differential between cue speed and CB speed after the millisecond (or whatever) of contact.

There are videos that show both the contact time and the reduction in cue speed that I think either/both Bob Jewett and Dr_Dave have posted.

Regads,
Jim
 
Predator did some very high speed filming and the cue does slow down and the ball is long gone. A milli second seems right.
 
coopdeville said:
The general consensus seems to be that the dwell time of the tip
on the ball is ~1ms (millisecond) or 1/1000 of a second.

Back to billiards.
Without doing the math, it seems that the tip is in contact with
the ball for the first few inches of the CB:OB journey.
Maybe someone wants to do the math, I don't.
Click to expand...
I think the Jacksonville project illustrated the contact time in ultra-slow-mo. See here. And I'm certain Dr. Dave has also illustrated this. Try: HERE, HERE, HERE, HERE or HERE.

I believe your 1ms estimate is correct. I would bet the distance during contact is about 1/8" -1/4" or so. Maybe 1/2". But not much more than that.

Was there a question associated with this or just a statement in general?

Cheers,

-td
 
Last edited:
td873 said:
I think the Jacksonville project illustrated the contact time in ultra-slow-mo. See here. And I'm certain Dr. Dave has also illustrated this. Try: HERE, HERE, HERE, HERE or HERE.

I believe your 1ms estimate is correct. I would bet the distance during contact is about 1/8" -1/4" or so. Maybe 1/2". But not much more than that.

Was there a question associated with this or just a statement in general?

Cheers,

-td
Click to expand...

I'll bet on 1/4 in.

And your avatar really....ummmmm....BUGS me! (-:

TOO FUNNY! I went to squash it with my thumb...TWICE!! Thanks for the chuckle.

(-:
 
more croquet

This is what I thought was really interesting.
link
The contact time between mallet and ball is as short as .09ms,
and as long as 4.5ms.
coop, just looking for more input
 
cue tip contact time and distance

FYI, cue tip contact time info can be found here:
For typical pool shots (1-10 mph) and typical contact times (about 0.001 sec), the tip is in contact with the CB for less than 1/4 inch.

Regards,
Dave

coopdeville said:
The general consensus seems to be that the dwell time of the tip
on the ball is ~1ms (millisecond) or 1/1000 of a second.

This is interesting to me because, in golf, the dwell time is considerably
shorter at ~.5 ms. Yet in that ~.5 ms, while the club is in contact with
the ball, the club has moved the whole way through the ball.

Even in tennis, with a soft ball, the contact time is only ~5 ms.
Croquet, ~1 ms.
In croquet, tests have been done that show a variance in the
contact time upwards of 2ms.
The numbers that I saw were 1.5-3.7 ms. depending upon what type
of stroke was used.

Back to billiards.
Without doing the math, it seems that the tip is in contact with
the ball for the first few inches of the CB:OB journey.
Maybe someone wants to do the math, I don't.

Here's one link with some reference and interesting points about
the physics of croquet vs golf. Link
I'll add another one later.
Click to expand...
 
dr_dave said:
...For typical pool shots (1-10 mph) and typical contact times (about 0.001 sec), the tip is in contact with the CB for less than 1/4 inch.
Click to expand...
Dr. Dave,

I think Patrick is closest with his measurement of 1/8". In the case where the cueball comes off at only 1.3X stick speed because of compression losses (instead of 1.5X), I believe its time averaged speed during the collision would be about 1.15X its final speed divided by 2 (it would be 1X this in a perfectly elastic collision). So if its final speed is, say, 10 mph (=176.0 in/sec), and contact time is .001 sec, it should move about 1/10".

(I know it's a nitpick, but since people are trying to get it within some fraction of an inch....)

Jim
 
Last edited:
how about with a kamuii tip

With a no proporsity tip will it be more or less? thanks How about with the ob-1 shaft, stiff and a no-proporsity Kamuii II Hard. I think good topic and I should ask as well, with a Pred 314-2 or z-2, thats three more questions. thanks for any generated responces mark
 
short tip contact distance

Jal said:
Dr. Dave,

I think Patrick is closest with his measurement of 1/8". In the case where the cueball comes off at only 1.3X stick speed because of compression losses (instead of 1.5X), I believe its time averaged speed during the collision would be about 1.15X its final speed divided by 2 (it would be 1X this in a perfectly elastic collision). So if its final speed is, say, 10 mph (=176.0 in/sec), and contact time is .001 sec, it should move about 1/10".

(I know it's a nitpick, but since people are trying to get it within some fraction of an inch....)

Jim
Click to expand...
Jim,

I wasn't trying to provide a specific answer for a specific shot because tip contact time and distance varies some with shot speed and tip hardness. I was just trying to reinforce that the contact distance is much smaller than some people think. I agree that typical contact distances will be much less than 1/4 inch.

Regards,
Dave
 
coopdeville said:
This is what I thought was really interesting.
link
The contact time between mallet and ball is as short as .09ms,
and as long as 4.5ms.
coop, just looking for more input
Click to expand...
I think you have a decimal point off in the low case. For the high end of contact time, I suspect the players are using the equivalent of a push shot.
 
coopdeville said:
The important factor that I see isn't the distance, it is the difference
in time of contact.

Bob,
The .09ms came from the link that I provided.
Here it is again.
http://www.oxfordcroquet.com/tech/hall/index.asp
You're right about the push but standard shots are up to 4ms.

-cOOp
Click to expand...


And he's right about the 0.09 really being 0.9, imo. It's pretty clear from the tales of numbers in the link you provided.
 
Seems to me that the methodology of this test was highly flawed.

"For this purpose, a few strands of copper wire were wound around the ball. At right-angles to this, a strip of aluminium foil was fixed to the ball. Foil was also taped to the end faces of the mallet. The two metal surfaces were connected to an electronic timer so that when the surfaces were in contact the timer was operational."

Introducing copper wire and aluminum foil to the contact area absolutely altered the true dynamcis of the contact...the only issue being to what extent.

Super slo mo video of the actual surfaces contacting each other is a far more definitive approach IMHO.

Regards,
Jim
 
klockdoc said:
Question..:confused:

Is the cue shaft rising up after contacting the CB in this video
1). result of the tip being hit towards the top of the CB, or,
2). a result of the shooter follow through?
Click to expand...

I vote for #1... the upward motion of the cue is a result of Newton's Third Law of Motion... For every action there is an equal and opposite reaction.

The contact point of the cue with the ball is such that the bottom of the tip strikes the ball (due to the follow that's imparted on the cue ball)... and therefore the cue tends to rise up due to the vector of the contact force being up and to the left (relative to the cue's tip).
 
klockdoc said:
Question..:confused:

Is the cue shaft rising up after contacting the CB in this video
1). result of the tip being hit towards the top of the CB, or,
2). a result of the shooter follow through?
Click to expand...


Definitely # 1

the tip on a whippy shaft might go up twice as far as one on a stiff shaft
 
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