Impulse Question for Horton

[rwh]

Horton:

A few weeks back you posted that force is applied to the ball ”through Impulse”. I couldn't recall what "Impulse" means, so I did some research and came across the following statement on the Physics Classroom site:

"In a collision, an object experiences a force for a specific amount of time which results in a change in momentum (the object's mass either speeds up or slows down). The impulse experienced by the object equals the change in momentum of the object. In equation form, F * t = m * Delta v."

I assume the equation states: Force x Time = Change in Momentum.
I also assume that the greater the Change in Momentum, the farther the ball flies [other variables being constant].

It would seem that increasing the Time the ball is on the clubface could translate to more distance. If I'm correct so far, is there anything a player can do to increase the time the ball spends on the clubface -- or will that always be a constant [assuming the same club and ball is used on all tests].

Thanks in advance. I have no agenda with this -- just an honest question.

 

[Jim Kobylinski]

rwh...it's called sustaining the line of compression with no leakage or in layman terms:

smash factor

Keep the smash factor up and ball speeds will be up...its about efficiency

 

[horton]

rhw::

Regarding your question about increasing Impact duration, that will vary with ball construction and clubhead construction, positioning and velocity. However experimentation indicates it always hovers around 400 microseconds.

Why are you concerned about how long the ball stays on the face of the club? I ask this question because scientists using more complex equations covering many factors have studied ball-club impact behavior and have published the results of their studies in Science & Golf II and III. I counted 14 papers presented at the World Scientific Congress of Golf and in each of these papers, the nature of ball-club collision is highly complex with as many as 6 parameters being tested.

A particularily interesting study was done by S. Ujihashi of the Tokyo Institute of Technolosy, Faculty of Engineering entitled -- Measurement of dynamic characteristics of golf balls and indentification of their mechanical models. From this 1994 study:

"However as far as the period of contact is concerned, a significant difference is observed between wound balls and two-piece balls, that is, wound balls have a longer period roughly by 15% than two-piece balls .... " (400 versus 460 microseconds!)

"At a level of low impact velocity such as 30 m/s the ball behaviour is almost perfectly elastic. Hoewever as the velocity increases the response becomes more and more visco-elastic and energy absorpton by the deformation of the ball is outstanding. This fact corresponds with that the restitution coefficient reduces and the impact velocity increases."

So you see, rwh that attempting to determine if the duration of Impact is longer with higher clubhead velocities is too simplistic and fraught with misinterpretation. Homer tried to touch on ball deformation based on his layman's understanding of pre-1980 science and came up with the faulty concept of LOC ...... which devout believers think is the last word in golf science. Science advances while Homer doesn't.

(p.s. -- a microsecond is one-millionth of a second!!)

 

[rwh]

Horton:

Interesting stuff and thank you. I guess I'm trying to understand if it is possible to make the ball stay on the face longer without increasing the force. Are you saying that if Golfer X hits a large bucket of identical balls using the same 5 iron, the ball is going to stay on the face of the club the same amount of time, every time, regardless of whether he's hitting a good or bad shot?

 

[horton]

quote:Originally posted by rwh

Horton:
I guess I'm trying to understand if it is possible to make the ball stay on the face longer without increasing the force.

Are you saying that if Golfer X hits a large bucket of identical balls using the same 5 iron, the ball is going to stay on the face of the club the same amount of time, every time, regardless of whether he's hitting a good or bad shot?

Good questions, and I wish I had a good answer for you. From my reading of the various tests done on golf balls it seems as if you can't get too much variation from 400 microseconds contact duration regardless of force in a reasonable range of application. These studies were done with good square impact contact so it might be safe to assume that bad shots will mess up contact duration because sliding forces will increase while sticking forces will drop. It's all in the complex force analysis and changing dynamic characteristics.

Again, why the concern for impact duration? The quality of impact should be your concern and that will result in an optimal duration time ... which incidentally is too short for concern. If you want to feel that impact satisfaction of perceived extended duration, you should use the softest golf balls availiable ... somewhere in the 50 Compression range and marketed for that exact sensation.

It seems that not only are you trying to "feel the lag" you are also may be trying to "feel the bash" to get that satisfaction sought by all golfers.