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´teached yourself some fancy words, but you dont know their

Posted: Fri Jun 12, 2009 7:40 am
by hkj
Shooting Kiwi wrote: It all depends upon what is meant by 'recoil'. If one means recoil force, then f=m*a, as you say, but one might be considering recoil impulse or energy or momentum. Or, indeed, their derivatives or integrals. It can all get very complicated,
Ha!: Recoil impulse orenergy or momentum..(!)
Recoil impulse and momentum, you say? That´s the same thing.....:-).

Ha! Integral of what? Integral of momentum? You must be kidding. Just about nonsence.

Derivatives of what? Of energy? That´s simply Power. Streight forward. I learned that in shool at age 10 ..(or was I just 9?).

Complicated? No, not really. It may seem complicated to you, but that is cause you are mixing up the nomenclature, and/or you don´t understand the fundamentals.

Buy yourself a fundamental textbook in Physics, and start reading...or, better, register for Physics 101 or Math 101 at your nearest college/university.
Just my 2 cents worth of advice...:-)

Posted: Fri Jun 12, 2009 8:36 pm
by Shooting Kiwi
hkj, your rudeness and arrogance does nothing to establish your credentials.

hkj wrote:
Recoil impulse and momentum, you say? That´s the same thing.....:-).
You are wrong. The impulse of a force equals the change in momentum produced by that force.

I appear to have a better grounding in mechanics than you believe.

For those still interested in this discussion, rather than just displaying their bovine nature, I would like to explore further just what characteristics of a gun's recoil are important, from the point of view of perception. Is it, for example, the ultimate velocity achieved by the gun, its achieved momentum, its rate of deceleration, the energy dissipated in stopping the gun's movement, etc., etc.? All of the above? I remain humble enough to admit that I don't know. Does anyone? If so, please tell us.

Post Subject

Posted: Fri Jun 12, 2009 8:44 pm
by 2650 Plus
I say again, This has nothing to do with shooting a ten, and if this is part of your thought process while you are shooting you may never shoot that ten. This discussion belongs in a college class room. Good Shooting Bill Horton

Re: Post Subject

Posted: Sat Jun 13, 2009 2:44 am
by David Levene
2650 Plus wrote:This discussion belongs in a college class room.
But isn't TargetTalk shooting's classroom.

This subject is obviously of interest to some, so this is the best place for it to be discussed.

No better grounding, no...

Posted: Mon Jun 15, 2009 6:49 am
by khj
Shooting Kiwi wrote:
Recoil impulse and momentum, you say? That´s the same thing.....:-).
You are wrong. The impulse of a force equals the change in momentum produced by that force.

I appear to have a better grounding in mechanics than you believe.

.
No, of course I am not wrong. Untill the gun is fired, there is no recoil! I think even you will admit that....And recoil force stops when the bullet has left the muzzle, and gas pressure equals ambient pressure.

So, the change is momentum is what my listed equation tells. ( If you substract zero from a given quantity, Kiwi, you get noe change of the quantity.....!)

Kiwi: did you think there was a momentum originating from discharge of gun before the gun was fired?LOL.

No, I am not impressed by your knowledge of math/physics. I am rather stunned by our own posted proofs of the opposite...:-)
Whoever wants to "integrate momentum" (you did in an earlier post) is way off. Dont´you think you have kind of disqualified yourself from any further discussion, Kiwi? I think so...:-)

Why I alternate the sequence of my initials? That is another bummer from you, Kiwi. Because I am ambulating around at more educational institutions, striving to teach students math/physics, using dirrent PCs, I have to alternate the sequence of my initials, cause, otherwise I am told by the TargetTalk program that " said guest-name is already in use".
I thought, cause you are trying very hard to convince me about your smartness, you were able to figure that out. I was wrong. I expected too much from you, Kiwi.

Me rude? Not at all ...:-) I am not "trolling", I just get agitated by your attempths to prove me wrong. Your chanses for proving me wrong in (elementary) physisc are small, ... I hope.

I am just disencouraged by the verlasting (perpetual) misunderstandings of those fundamentals in math/physics conserning. recoil. Even from people who ought to do better.

BTW, Kiwi, student these days are working harder than ever to grade well in said diciplines. That´s one positive effect of the financial crisis...

impulse

Posted: Mon Jun 15, 2009 4:59 pm
by Shooting Kiwi
Good grief! Good manners cost nothing. Apologies to anyone who is bored by this discussion and irritated by the rudeness latterly displayed, but misinformation should be corrected..

khj wrote:
No, of course I am not wrong. Untill the gun is fired, there is no recoil! I think even you will admit that....And recoil force stops when the bullet has left the muzzle, and gas pressure equals ambient pressure.
Well, I'm sorry to have to correct you again. The thread is about perceived recoil and has discussed the recoil primarily of blowback pistols, rather than other, locked-breech actions. In a blow-back action, the major contribution to the perceived recoil is the slide reversing its direction of travel as it slams back against the frame. This happens some time after the bullet has left the barrel.

The forces on the frame of a blow-back pistol are complex: the first applied force will be due to case-to-chamber friction. Previously in this thread, I have assumed this to be insignificant in .22 pistols, but I'm happy to see evidence to the contrary. This force acts directly on the barrel, thus directly on the frame. As the bullet is forced along the barrel, barrel friction causes a force on the frame in the opposite direction. As the bullet exits, the muzzle blast acts on the barrel. As the slide begins to recoil, it cocks the hammer against the hammer spring and compresses the recoil spring. These forces are reacted by the frame. As I've said, earlier in the thread, the cocking force varies dramatically with slide position, and some designs allow a 'smoother' cocking action than others. Therefore, the forces transmitted to the frame by trigger cocking will be quite different from one design to another. Slow-motion videos have been referenced, showing that, in spite of these forces acting on the frame whilst the slide is recoiling, the gun hardly moves in the hand, even after the bullet has left the barrel. It is when the slide hits the stop that the gun kicks in the hand.

My definition of the impulse of a force is text-book correct, as any student of elementary mechanics should know. Perhaps you are not familiar with this terminology: from your use of English, I suspect that English is not your native language. We may be arguing solely about semantics.

My admittedly loose use of 'derivative' and 'integral' was my musing that it is not clear from the literature just how importent, from a subjective point of view, are the various parameters of the recoil phenomenon. In other words, (and this is more musing, not tight, well-worded physics!) when we feel recoil, are we mainly conscious of the velocity of the gun, its momentum, the force applied to the hand, the rate of change of force or velocity (or anything else), the distance the gun moves in the hand, the energy dissipated in the hand, work done in compressing the tissues of the hand, etc., etc.? As I've said, I'm humble enough to say I don't know, but I do understand basic mechanics!

khj, rather than trying to make honest contributors seem fools, which is tedious and out of place in this forum, perhaps you could address the subject of the thread and enlighten us all. Most of us remain humble enough to listen with courtesy and eager to learn.

Re: impulse

Posted: Mon Jun 15, 2009 7:16 pm
by superstring
Shooting Kiwi wrote:Good grief! Good manners cost nothing. Apologies to anyone who is bored by this discussion and irritated by the rudeness latterly displayed, but misinformation should be corrected..

..........

khj, rather than trying to make honest contributors seem fools, which is tedious and out of place in this forum, perhaps you could address the subject of the thread and enlighten us all. Most of us remain humble enough to listen with courtesy and eager to learn.
+1, Shooting Kiwi. Whether you happen to be right or wrong about the physics, my hat goes off to you for maintaining a sense of decorum. You're certainly a better man than I would be under the circumstances.

halfwit

Posted: Tue Jun 16, 2009 4:01 am
by jsealc21
I'm with Superstring !

Re: impulse

Posted: Tue Jun 16, 2009 12:40 pm
by khj
Shooting Kiwi wrote: - perceived recoil is the slide reversing its direction of travel as it slams back against the frame. This happens some time after the bullet has left the barrel.
You are in a way right. But look into this situation: A tensioned recoil spring, that relaxes with forward slide motion, is doing "work", releasing stored potential energy, that is, by exerting force to the slide over some distance of slide travel, (conteracting some friction/inserting a new round into the chamber...) . A secondary consequense of recoil/rearward slide travel that is.

Imagine this brought even further: after the last shot, some pistols have an "action remains open after last shot" hook-up feature. Then your last part of "recoil" is in fact felt whenever the guns user desides to release the slide catch and let the slide move forward; - second, minutes, or even hours after tha last shot. That is then "delayed recoil".....:-)
Shooting Kiwi wrote: My definition of the impulse of a force is text-book correct, as any student of elementary mechanics should know. Perhaps you are not familiar with this terminology: from your use of English, I suspect that English is not your native language. We may be arguing solely about semantics.
German is my mothertongue. You have my regards for accepting my less than perfect English language.

But agin, may i most politely ask you to explain to me what use ther may be for your concept "integrated momentum". I am not able to follow you at that point. Or have I misinterpreted you at this point?

And to other readers: the elementary/basic physics we are dicussing here is equivalent to US "High Shool" level physics, I think. Easily understandable to anyone.
Shooting Kiwi wrote: My admittedly loose use of 'derivative' and 'integral' was my musing that it is not clear from the literature just how importent, from a subjective point of view, are the various parameters of the recoil phenomenon.
Ok, see your point.
Shooting Kiwi wrote: ... but I do understand basic mechanics!
Yes, you do. You are doing quite well, most of the time.
Shooting Kiwi wrote: khj, rather than trying to make honest contributors seem fools,.
Yes, you may be right. I appologize for my rude, and even offending statements. but my blood vessel pressure is upped whenever I see what may be interpreted as incorrect or inaccurate us of the Newtonians.:-)

Posted: Wed Jun 17, 2009 4:46 am
by Shooting Kiwi
(Sorry Guys, more esoteric rambling...)

khj,

Yes, I agree about the difference in recoil when the slide is held back, as occurs in some semi-autos, after the last round is fired. This produces such a different perception that this feature is usually now not incorporated into target pistols. I hope we agree that whether the slide is held back or allowed to return, the perceived main recoil of the gun in the hand happens after the bullet has left the barrel.

I should not have used the terms 'integral' and 'derivative' so loosely, particularly in the same sentence as 'momentum': it was idle musing, rather than careful physics. However, since you ask about the integral of momentum, the answer is easy.

[Integral] p dv = 1/2 mv^^2 ( + constant) = Kinetic Energy

In fact, exactly this definition of KE is used in the more rigorous derivations (and the more boring text books).

I fully agree that momentum integrated with respect to time ([Integral] p dt) is a pretty useless concept!

Thanks for your gracious apology. I think we agree about most of this, including my sloppy use of English.

Integral of momentun indirectly related to energy, but...

Posted: Wed Jun 17, 2009 11:03 am
by hkj
Shooting Kiwi wrote: I should not have used the terms 'integral' and 'derivative' so loosely, particularly in the same sentence as 'momentum': it was idle musing, rather than careful physics. However, since you ask about the integral of momentum, the answer is easy.

[Integral] p dv = 1/2 mv^^2 ( + constant) = Kinetic Energy

In fact, exactly this definition of KE is used in the more rigorous derivations (and the more boring text books).

I fully agree that momentum integrated with respect to time ([Integral] p dt) is a pretty useless concept!
Yes (and no...). According to Newton: m1*v1 = m2*v2 (equal, oppositely directed momentums.
Energy (kinetic) of a recoiling gun and an accelerating bullet(+ gases) are not equal.
Kinetic energies are (approximately) equal only if mass of gun (and powder charge) is equal to the mass of the gun,- an unusual situation! (imagine a RPG7 or M72 LAW propelled rocket launcher with the rear end of the launch tube totally blocked (welded shut) by a solid steel plate..:-).

The time-derivate of energy? That is Power, which is F*v... which again is not m*v.....:-)

Thanks for an interesting discussion.

Why momentum cannot be integrated directly to give kinetic E

Posted: Wed Jun 17, 2009 12:03 pm
by khj
Shooting Kiwi wrote:
However, since you ask about the integral of momentum, the answer is easy.

[Integral] p dv = 1/2 mv^^2 ( + constant) = Kinetic Energy
No, it is not that easy...sorry.

No hard feelings, Kiwi, but you kind of "have ben had". Sorry about that.
I made a trap for you (hope you will forgive me...).

It is a common, and steadily reoccuring misunderstanding by students, to think that kinetic energy can be calculated directly by simply integrating momentum with respect to time.
It cannot be, if you know the value of the momentum only. (If you know the velocity of the object, there is no need to complicate by calculating from momentum., btw..:-
)
I have just been encouraged by a friend to explain to interested readers in detail why:
Momentum is the PRODUCT of mass and velocity. Velocity is dependent of the mass. To calculate kinetic energy you have to know both mass and velocity, not the product only!

From Newton: m1*v1 = m2*v2= C (constant, value given)
To calculate kinetic energy Ke of object 1:
v1 = C/m1, hence: Ke1 = 1/2*m1*(v1 squared).

Further: Ke1 = 1/2m1*(C squared).

But, as I have stated, you are doing very well, most of the time.

Posted: Wed Jun 17, 2009 4:47 pm
by Shooting Kiwi
khj,

Read more carefully what I wrote!

I have already agreed that integrating momentum with respect to time does not equal kinetic energy, but if you integrate momentum with respect to velocity it does! As I stated previously, this is used as a formal derivation of KE = 1/2 m v^^2. I suggest you search the web for 'integral of momentum' if you don't believe me.

Now, can we stop this?