quote:

Originally posted by Cross L:
I am gonna buy HORSE futures-there are a hell of a-lot of them being beat to death in this thread. and surely we are gonna run into a shortage.



SSR

quote:

Originally posted by vapodog:

quote:

Originally posted by Cross L:
I am gonna buy HORSE futures-there are a hell of a-lot of them being beat to death in this thread. and surely we are gonna run into a shortage.



SSR

Hey.....I just wondered.....do they sell bullshit futures too!

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Originally posted by Hot Core:
And garden time is right around the corner.

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Originally posted by rcamuglia:

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Originally posted by jwp475:

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Originally posted by Kabluewy:
This is the stuff of the ages. It was figured out long ago. Why is it a matter of such debate?

http://csep10.phys.utk.edu/ast...ory/newton3laws.html

http://www.google.com/search?q...d=ie7&rlz=1I7SKPB_en

http://en.wikipedia.org/wiki/M...93energy_equivalence

http://en.wikipedia.org/wiki/Sectional_density

http://en.wikipedia.org/wiki/Kinetic_energy

http://en.wikipedia.org/wiki/Projectile

http://en.wikipedia.org/wiki/P...al_projectile_speeds

http://en.wikipedia.org/wiki/KE-Munitions

http://en.wikipedia.org/wiki/Momentum


KB

You are exactly right, it all goes back to Newton's 3 laws of motion.

I doubt that these internet key board commando experts will even click on the links provided.

So I'll post one of them:

quote:

http://csep10.phys.utk.edu/astr161/lect/history/newton3laws.html

Newton's Three Laws
of Motion

--------------------------------------------------------------------------------

Let us begin our explanation of how Newton changed our understanding of the Universe by enumerating his Three Laws of Motion.

Newton's First Law of Motion:
I. Every object in a state of uniform motion tends to remain in that state of motion unless an external force is applied to it.

This we recognize as essentially Galileo's concept of inertia, and this is often termed simply the "Law of Inertia".

Newton's Second Law of Motion:
II. The relationship between an object's mass m, its acceleration a, and the applied force F is F = ma. Acceleration and force are vectors (as indicated by their symbols being displayed in slant bold font); in this law the direction of the force vector is the same as the direction of the acceleration vector.

This is the most powerful of Newton's three Laws, because it allows quantitative calculations of dynamics: how do velocities change when forces are applied. Notice the fundamental difference between Newton's 2nd Law and the dynamics of Aristotle: according to Newton, a force causes only a change in velocity (an acceleration); it does not maintain the velocity as Aristotle held.

This is sometimes summarized by saying that under Newton, F = ma, but under Aristotle F = mv, where v is the velocity. Thus, according to Aristotle there is only a velocity if there is a force, but according to Newton an object with a certain velocity maintains that velocity unless a force acts on it to cause an acceleration (that is, a change in the velocity). As we have noted earlier in conjunction with the discussion of Galileo, Aristotle's view seems to be more in accord with common sense, but that is because of a failure to appreciate the role played by frictional forces. Once account is taken of all forces acting in a given situation it is the dynamics of Galileo and Newton, not of Aristotle, that are found to be in accord with the observations.

Newton's Third Law of Motion:
III. For every action there is an equal and opposite reaction.

This law is exemplified by what happens if we step off a boat onto the bank of a lake: as we move in the direction of the shore, the boat tends to move in the opposite direction (leaving us facedown in the water, if we aren't careful!).

Notice that Newton's 3 laws of motion deal with momentum, momentum transfer, and acceleration. NO ENERGY RELATIONSHIPS.

Prove this wrong Vapodog and Hotcore.

I'd like to know how any of the three shows that kinetic energy is bogus as compared to momentum when evaluating rifle chambering's effectiveness on game?

If anything, the third law validates KE

A bullet with greater KE will have an equal but opposite reaction when it impacts...

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RVmedicNov27-05, 01:07 PM
I'll try to explain this to the best of my knowledge, which is limited and firearm related.:biggrin:

Kinetic energy is a magnitude. It only describes how hard an object in motion will hit another object and is expressed in foot pounds. Momentum is the application of kinetic energy and is expressed in joules, foot pounds per second, etc..... When comparing moving objects that are similar (IE, bullets of different weights and velocities), the projectile with more momentum would tend to move its target father regardless of kinetic energy.
Example.... A rimfire rifle is fired at a steel plate at 50 yards. If you hit it, it flips over. You have a choice of using a rifle that will propel a 40 grain bullet at 1249 f/p/s, or a 17 grain bullet at 2199 f/p/s at 50 yards (these are actual figures). If you only used the formula for KE, you would find the bullets would provide 139 ft-lbs & 183 ft-lbs respectively, so you would likely pick the bullet with the higher KE for the task at hand. Looking into the figures a little more, by figuring momentum.......the 40 grain bullet would provide 7.14 ft-lbs/second, and the 17 grain bullet would provide 5.34 ft-lbs/second (weight/7000*velocity). The heavier, slower bullet would be more likely to flip the plate because it has more momentum even though the lighter faster bullet has 44 more ft-lbs of kinetic energy.

Hope this helps....

As for why figures are squared, lets just say that the formulas are hard enough to remember as it is. Knowing why will just confuse me more....:surprised

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There are three different kinds of collisions, however, elastic, inelastic, and completely inelastic. Just to restate, momentum is conserved in all three kinds of collisions. What distinguishes the collisions is what happens to the kinetic energy.

Types of collisions: (momentum is conserved in each case)

elastic - kinetic energy is conserved
inelastic - kinetic energy is not conserved
completely inelastic - kinetic energy is not conserved, and the colliding objects stick together after the collision.
The total energy is always conserved, but the kinetic energy does not have to be; kinetic energy is often transformed to heat or sound during a collision.

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Given two arrows of equal momentum, but with one deriving a greater portion of its momentum from mass than the other, the heavier arrow will change velocity (decelerate) at a slower rate as it passes through the tissues. In other words, the heavier arrow will retain a higher percentage of its impact velocity at any given time period during its passage through the animal’s tissues, thus it also retains a higher momentum at any given point during the time required for the arrow to penetrate.



Another way of saying this would be that, though the heavier arrow is traveling slower, it takes a longer time to stop. The result is that the heavier arrow will have a greater impulse of force than does the light arrow.

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As the arrow’s velocity is increased the resistance does not increase equivalently. The resistance increases exponentially. The resistance of a medium to penetration is reliant on the square of the object’s velocity (assuming objects of a given coefficient of drag; i.e., using arrows with the same external profile, material and finish). In other words, if the arrow’s impact velocity doubles, the resistance increases by a factor of four. If the impact velocity quadruples, the resistance to penetration increases 16 times!



The effect of exponentially increasing resistance is easy to experience. Try holding a hand out the window of the car, while the car is going at a velocity of 30 miles per hour (which is only 44 feet per second), and feel the air’s resistance against your hand. The resistance is very slight. Now accelerate to 60 miles per hour (a mere 88 feet per second). The velocity has only gone up by a factor of two, but the air’s resistance to your hand passing through it is now four times greater.

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ALL MOMENTUM IS NOT THE SAME



Given two arrows, identical in shaft and broadhead materials and profile, and having EQUAL momentum, but possessing UNEQUAL mass, the arrow deriving the greater portion of its momentum from its mass will penetrate better. The Laws of Physics requires this to be true, and ALL of my field test data validates this to be the case.



To say this in another way, arrow momentum derived through increasing arrow mass results in a greater gain in penetration than does momentum gained by increasing an arrow’s velocity. This is true because the tissue’s resistance is increased by the square of the velocity.





Let’s look at two arrows of equal momentum, but unequal mass, both of which expend all their available net force in the tissues. If the momentum is equal between two arrows at impact, the one with the greater mass has to be traveling at a slower velocity. As shown above, the slower arrow will be met by a lower resistance force than the faster arrow.



With the momentum of the two arrows equal at impact, their disposable net force will be equal, but the resistance force will be greater upon the faster arrow. Because of the higher resistance force, the faster/lighter arrow will lose velocity more rapidly, and its momentum will diminish at a faster rate than that of the heavier arrow. It will stop in a shorter period of time, thus it will have a lower impulse of force than the heavier arrow.

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An arrow’s momentum is also a part of the arrow’s kinetic energy - the only part that relates to its ability to penetrate. Some of an arrow’s kinetic energy is dissipated as other forms of energy during flight and on impact. Even the ‘sound’ of a hit is derived from the arrow’s kinetic energy.

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Kinetic energy is frequently used as a guide to the potential lethality of a high speed bullet. This is because a bullet can cause tissue damage in ways an arrow can not.



Bullets carry massive amounts of kinetic energy, relative to an arrow. Much of a bullet’s kinetic energy is transferred through the tissues as a ‘shock wave’, caused by the rapid compression of tissue fluids.



As the bullet strikes, a ‘hydraulic force’ is transferred, through the tissue fluids, over a wide area. This causes histologic tissue shock, disrupting tissue functions. It is this hydraulically induced ‘shock wave’ that causes the ‘bruising’, or ‘blood-shot’ tissues surrounding a bullet induced wound channel.





If one researches the literature of terminal ballistics and killing power of firearms, they will find that, even there, the use of kinetic energy as an indicator of bullet lethality falters badly as the size of the animal increases. Its usefulness also diminishes with firearms producing low (by firearms standards) kinetic energy, as with handguns. This is the reason that such other ‘indicators’ of bullet lethality as “Taylor’s Knock-Out Value”, the “Optimum Game Weight” and the “Power Factor” find their way into firearms literature, all of which place more emphasis on the bullet’s momentum and/or impulse of force.


Studies conducted by the U. S. Army’s Ballistics Research Facility indicate that tissue shock from hydraulic compression becomes a significant “wound factor” only at impact velocities around 2500 feet per second, or greater. Creating ‘hydraulic shock’ is not an option with an arrow).

Kinetic energy is NOT the correct unit of measure for calculating ANY of the forces relevant to penetration. It is applicable for calculating neither the force of a moving object; the disposable net force at impact; the net force at exit; net force consumed during penetration; the applied impulse; nor the resistance impulse force affecting penetration.

With a given arrow, if its kinetic energy is increased, there will be a measurable increase in its penetration, but only because the velocity increase necessary to achieve more kinetic energy has also increased the arrow’s momentum. The increase in penetration will not be proportional to the increase in kinetic energy. It will be proportional only to the resultant increase in the arrow’s momentum (with the increased resistance created by the higher velocity also factored in).

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To me, it clearly shows what we all know about bullet construction/velocity. The higher velocity you shoot a projectile, the better the construction of that projectile needs to be. It also confirms my belief that a smaller caliber projectile of tougher construction will still have enough "power"(Energy/Momentum) to penetrate to the vital kill area, but not have "knock down power" (Momentum). Kinda like a 450 grain projectile going 285 fps completely passing through an animal but not blowing it down (an arrow).

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Kinetic energy is NOT the correct unit of measure for calculating ANY of the forces relevant to penetration. It is applicable for calculating neither the force of a moving object; the disposable net force at impact; the net force at exit; net force consumed during penetration; the applied impulse; nor the resistance impulse force affecting penetration.

With a given arrow, if its kinetic energy is increased, there will be a measurable increase in its penetration, but only because the velocity increase necessary to achieve more kinetic energy has also increased the arrow’s momentum. The increase in penetration will not be proportional to the increase in kinetic energy. It will be proportional only to the resultant increase in the arrow’s momentum (with the increased resistance created by the higher velocity also factored in).

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... momentum can be calculated but can also be measured (via a ballistic pendulum) ...

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Originally posted by 303Guy:

quote:

... momentum can be calculated but can also be measured (via a ballistic pendulum) ...

The ballistic pendulum is also a calculation. Well, I suppose if its calibrated it would give a direct reading but it could also be calibrated to give a direct kinetic energy reading. Anyway, it's a complex subject with significant implications and so many variables - that's what makes it so interesting and challenging. I've just seen some critters getting shot and some died on the spot while others took a while to let go of life and fall out the trees and yet another took off like there was a dog after it - wait, there was a dog after it! All hit with subsonic 22lr's. The variable was bullet placement and passage through the critter.

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Kinetic energy is to momentum what time is to space.

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Originally posted by Bear in Fairbanks:
This thread has been going on for so long and for no reason that my opinion, such as it is, is that it's all

And I'm still gonna keep using my .338 mag. on moose and my .27 cal. rifles on my sheep, caribou & hopefully maybe an interior grizzly.
Ya'll have a good day now.
Bear in Fairbanks

quote:

Originally posted by Bear in Fairbanks:
This thread has been going on for so long and for no reason that my opinion, such as it is, is that it's all

And I'm still gonna keep using my .338 mag. on moose and my .27 cal. rifles on my sheep, caribou & hopefully maybe an interior grizzly.
Ya'll have a good day now.
Bear in Fairbanks

quote:

Originally posted by Bear in Fairbanks:
This thread has been going on for so long and for no reason that my opinion, such as it is, is that it's all

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Most physics textbooks provide a simplified method of calculation that uses the mass of the bullet and pendulum and the height of the pendulum's travel to calculate the amount of energy in the pendulum, and thus the amount of momentum in the system.

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To use the pendulum, it is set up with a device to measure the horizontal distance of the pendulum swing, such as a light rod that would be pushed backwards by the rear of the pendulum as it moved. The shooter is seated at least 15 feet (5 m) back from the pendulum (reducing the effects of muzzle blast on the pendulum) and a bullet is fired into the pendulum. To calculate the velocity of the bullet given the horizontal swing, the following formula is used:[7]

V = \frac{Mp}{Mb}0.2018 D

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Originally posted by 303Guy:

quote:

Most physics textbooks provide a simplified method of calculation that uses the mass of the bullet and pendulum and the height of the pendulum's travel to calculate the amount of energy in the pendulum, and thus the amount of momentum in the system.

The momentum is still being calculated, not directly measured.

P. O. Ackley's ballistic pendulum.

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To use the pendulum, it is set up with a device to measure the horizontal distance of the pendulum swing, such as a light rod that would be pushed backwards by the rear of the pendulum as it moved. The shooter is seated at least 15 feet (5 m) back from the pendulum (reducing the effects of muzzle blast on the pendulum) and a bullet is fired into the pendulum. To calculate the velocity of the bullet given the horizontal swing, the following formula is used:[7]

V = \frac{Mp}{Mb}0.2018 D

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Originally posted by ClassicAl:
Wstrnhuntr:

You must be either a youngster, or just don't hang out in the right forums .

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Originally posted by scottfromdallas:
This seems like a perfect thread for Warrior. I'm surprised he has not chimed in.

I don't get caught up in numbers anymore. I look for an appropriate sized bullet for the game I'm going to be hunting and I look at a reasonable velocity for expansion at the distance I plan to be shooting.

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Guys, we really must release our voodoo hold on all these unwilling readers. Before you know it, we'll be arrested for unlawful imprisonment in an internet forum.

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Originally posted by someoldguy:
IMO you really have to be careful when you're looking at both energy and momentum figures, Red. Well, not so much careful as knowing how to interpret them.
I'm sure you're aware you've already identified where you can go wrong when you focus only on energy. You'd think a .243 with an 80 grain bullet is more effective against game in general than a .30-30. Both experience and commonsense will likely show this isn't the case in the real world. (I've never used a .243, but I've heard cautions about using bullets lighter than 100 grains against deer. As for the "boring old" .30-30, we should already know about its success on deer!)
Momentum can also mislead you, if you let it. If you're using it to estimate penetration, you have to remember than penetration is inverse to the penetrating surface area. In other words, the more surface area you have, the less penetration you'll have. And that's just commonsense really.
The reason I do all this is for my own sake. And it's not intended as a substitute for actual experience in the field. I do this to try to get an intuition, but one based on scientific/physical/mathematic principles and not "magic" or rumor.

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There is more to terminal penetration than mere surface area.

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The reason I do all this is for my own sake. And it's not intended as a substitute for actual experience in the field. I do this to try to get an intuition, but one based on scientific/physical/mathematic principles and not "magic" or rumor.

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However, there is one other factor to be considered. One might be willing to give on the momentum in favor of the flatter trajectory the faster bullet affords (if it maintains enough killing power to to the job adequately).

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There is more to terminal penetration than mere surface area.

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I read somewhere of a penetration test in which it
as found that a bullet that forms a mushroom creates a vapour cavity trailing off the edge of the mushroom that prevents flesh and liquid from disturbing the nose forward attitude.

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Originally posted by someoldguy:

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There is more to terminal penetration than mere surface area.

Yet another example of reading only one bit of what someone wrote and taking it completely out of context just to disagree with them. Arguing just for the sake of arguing. Pathetic.

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I read somewhere of a penetration test in which it
as found that a bullet that forms a mushroom creates a vapour cavity trailing off the edge of the mushroom that prevents flesh and liquid from disturbing the nose forward attitude.

I don't know about the vapor cavity. Maybe they're right. But it's pretty much common knowledge that mushrooming or expanding bullets don't penetrate nearly as well as their solid counterparts.

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Originally posted by someoldguy:
IMO you really have to be careful when you're looking at both energy and momentum figures, Red. Well, not so much careful as knowing how to interpret them.
I'm sure you're aware you've already identified where you can go wrong when you focus only on energy. You'd think a .243 with an 80 grain bullet is more effective against game in general than a .30-30. Both experience and commonsense will likely show this isn't the case in the real world. (I've never used a .243, but I've heard cautions about using bullets lighter than 100 grains against deer. As for the "boring old" .30-30, we should already know about its success on deer!)
Momentum can also mislead you, if you let it. If you're using it to estimate penetration, you have to remember than penetration is inverse to the penetrating surface area. In other words, the more surface area you have, the less penetration you'll have. And that's just commonsense really.
The reason I do all this is for my own sake. And it's not intended as a substitute for actual experience in the field. I do this to try to get an intuition, but one based on scientific/physical/mathematic principles and not "magic" or rumor.

quote:

I appreciate your post. However, I didn't intend to say that the .243 was better for deer hunting than the .30-30, but rather, on paper, using energy alone to evaluate the two, the ballistic tables (specifically energy) really make the .243 with an 80 grain projectile LOOK/SEEM to be much better than the .30-30. I totally agree with you that the 80 grain bullet in the .243 in actual field use hasn't demonstrated itself to be a great deer taker.

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Originally posted by someoldguy:
Confusing stuff sometimes.

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Originally posted by Red C:
...Also, I believe, in the real world of hunting, one might be willing to sacrifice a little momentum in favor of a flatter trajectory that some smaller, faster bullets afford (as long as you still have adequate killing power).

Location of vitals

No matter the trajectory of a projectile of a given cartridge, one can still put the bullet accurately on target by any number of methods; dialing data, holding over with a ballistic reticle. It wouldn't make sense to shoot a 22-250 at Oryx simply because it is flatter shooting and will increase your ability to make an accurate shot placement at longer ranges (The .223 for deer contingent will argue with that ). Now choosing the 7mm RUM for the task makes sense. Same trajectory as the 22-250 with lots of energy/momentum because of a heavy bullet going really fast.

If a proponent of small calibers for big game does any type of long range target shooting, he will soon see through experience the advantage of shooting heavy bullets for game as well.

Higher Sectional Density

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Higher Sectional Density