Home Forums Hunting & Shooting Elk Hunting Enough energy for elk?

Huh?? Surely you jest..

Without a transfer of energy, there is no applied force, no hydraulic pressure created.

With an infinite transfer of energy, the animal, the earth and the universe are destroyed.

Everything else is just a shade of grey.

The book (Fackler?) states mistakenly states:


As I said, energy is a tool that can be used or abused. I take issue with the use of the term "any".

If I am hunting elk and have two 180g .308� loads, I would much rather use the load that retains energy of 3000fpe at expected impact ranges than the load that only carries 500fpe at the same range. Both might (and should) kill with proper placement but the former will likely expand more reliably and do much greater damage.

Your argument would be that one could not look at the differences in retained energy and come to a useful conclusion as to which would be the better elk cartridge. That is like saying you can�t determine which would be better for thirsty crops, a light sprinkle or a good soaking rain, because they both provide moisture. Lots of farmers would disagree.

Well Coyote Hunter I am going with what Duncan McPhearson states in his book since he graduated from MIT with honors and has the only Ballistics model that has been proven to accurately predict the wound channel size and penetration and the model was proven to work 100% of the time bu Dr. Martin Fackler President of The International Wound Ballistics Assoc. and former Head Of The Army Wound Ballistics Lab and they both discount energy transfer.

The fact is in a collision(which is what a bullet impact is) ENERGY DOES NOT TRANSFER, and that is a fact whether or not you wish to accept it or not


If Energy transfered then Newtons Laws of Motion would be invalid, which they are not

That is correct you can not properly rank terminal performance by useing FPE. My 338 Lapua with the 300 grain SMK at 2791 FPS makes 5188 FPE at the muzzle a 458 win with a 500 grain bullet at 2100 FPS makes 4896 FPE to sugest that the 338 is a better Elephant round is ridicules. The 458 500 grain bullet has more momentuma nd more direct applied force and can transfer more momentum

A 22-250 with a 55 grain bullet at 3600 FPS has 1582 FPE, a 360 grain WLFN flat point hard cast in a 454 Casull at 1400 FPS has 1567 FPE. That is less than the 22-250, is that your choice to stop a mad Grizzly Bear? Certainly is not my choice, yet the 22-250 has more energy. Energy can not be measure it can only be calculated.
In a collision energy is calculated in Joules, which is a heat measurement. Why is that? It is because FPE transforms into thermal energy (heat)

1 Joule is equal to 0.737562149 FPE

I knew I was going to regret reading this thread.....

As a mechanical engineer myself, I would like to understand how the above statement is true. Unless we are getting picky on terminology. I would also like to understand how Energy has nothing to do with the discussion.

Physics is physics right?

Impact / Momentum = mv1 + mv2 = m'v'1 + m'v'2
Energy = 0.5*mv^2 + Q + W + mgh

Seeing that there is as we have called it "Soft Tissue" in this equation, there is an inelastic sinario.
So before impact you have m and v of the bullet which gives you both momentum and energy. You can't have momentum without energy. So both are definite factors and can't be ignored.

After impact, your bullet velocity may essentially go to zero while your bullet mass may be still constant....so at that point your bullet no longer has momentum or energy due to the velocity being zero. Where the heck did they go if they were not transfered or converted? Looking at our laws of physics, you must do a mass energy balance. So if the bullet no longer has that momentum or energy and it is not transfered or converted, our laws of physics are crap.

In theory it could have all instantaneously converted to heat (Q), but that would most likely mean that your hole would be cauterized. I tend to think that letter "W" (work) comes into play since the potential energy (mgh) is not really factor here.

Shoot...I have to run to a meeting. Again, I would just like to understand where the energy and momentum went when the bullet decelarated from X fps to zero.

ME here also and I've already tried to reason with them.

What no shock wave?

The "shock wave" happens when energy transfer is too rapid or high rate to be absorbed by the target or target area. Heat something and it absorbs, now heat it till it glows, presto light "wave"...similar idea.

I will concede that shock may make little or no difference in big game killing.

I don't care....shock wave, no shock wave. Shock and/or wave may or may not be the right wording. Whatever.

But physics is physics sir Isaac.
The energy and momentum, which in this case are the start by a bullet of mass "m" flying at a velocity "v", are the inputs to the calculation/formula. They don't just magically disappear and cannot be ignored or be considered a non-factor. Energy cannot disappear......its physics. If you consider momentum a factor, you cannot consider energy a non-factor.

If someone says that they had a bullet pass through and exit at the same speed as it entered and therefore retains all of its energy....I guess I can't argue with the calculation behind it, but would like to see it since in theory even the air it is passing through is slowing it down.

If someone says that all of the energy converted entirely and immediately to heat.....I guess I can't argue with the calculation behind that either, but I have yet to see a deer or elk have cauterized holes.

So once again, where does it go? If we exclude the upper two sinarios since they are not reasonable, where does that 1000ftlbs or 2000ftlbs of energy go remember that you cannot have momentum without energy?

If someone says that it is a combination of heat and work, I will start to bite. We all know what heat is. Work is what? Moving something a distance is work right?
If that work is displacing the tissue in the way of the bullet path, I'll stay interested. If that displaced tissue once again has to transfer/convert energy due to its mass at a new velocity being decelerated, this energy will again transfer/convert heat and work to the neighboring tissue. This will continue to happen until there is essentially no more work being created and all of the heat is dissipated.
I don't care what its called...shock wave, hydrowhatever.

My question is, where does this energy go since it cannot and will never dissappear?

In a collision energy transforme into other forms of energy mostly thermal. Being an Engineer I am sure that you are familar with Newtons Laws of Motion. Momentum transfers in a collision, not energy.

McPhearson devotes and entire chapter to understanding this. Buy the book

Don�t you love it when people argue that momentum is conserved but pretend energy doesn�t matter, even though it is also a conserved entity and inseparable from momentum in that you either have both or you have neither?

Don�t you love it when they claim no energy is transferred to the target but have no answer for where it goes when the bullet�s velocity, and therefore its momentum and energy, drops to zero? Maybe they think it just disappears? (So much for conservation...!)

The fact is that it takes WORK to tear flesh asunder, shatter bones and do the other things a bullet does. Maybe they think when a prairie dog is sent flying is different directions the energy required to accelerate the body parts comes from a lightning bolt?

While I freely admit that energy alone is a poor predictor of terminal performance, it is a tool with its place, to be used or abused as the user sees fit. The more similar the calibers and bullets the more useful it becomes, and vice versa. As I�ve said many times, though, retained energy is only one aspect. More important is the rate at which energy is transferred and for what period of time, something retained energy figures alone cannot inform about. Then there is bullet weight, bullet construction, etc., all factors that play a part in terminal performance.

The truth remains, however, a bullet with zero energy does no harm while a bullet with infinite energy destroys the target, the earth and the universe.

I will butt heads with JWP no more; y'all have my sympathy.

THIS Luddite thought one definition of energy was " the ability to do work". In this case, the work is to crush, tear, bruise, and liquefy various tissues. No? Otherwise, the only difference between the wound from a .30 Carbine and a .30 RUM would be the length.

Second point... Ask a prairie dog about the non-existance of "shock waves" after he's been popped over a 100 sq/yd area... Methinks there's a wee little prarie dog in the vitals of every big animal just waiting to be popped... Just sayin'...

Again Jeff O misunderstands that the Prarrie Dog is ripped appart by the hydraulic pressure that is too great for it's mass. Shoot a Prarrie Dog with a 22-250 bullet at 3600 FPS and watch the explosion. Shoot one with a 360 grain bullet at 1400 FPS (roughly the same FPE) and NO Explosion

Kinetic energy is transformed into thermal energy in a collision. Agains Newtons Laws of Motion deal with 1- Forces, 2-Momentum transfers, 3-Acceleration, not energy relationships.

1 Foot Pound of energy is equal to 1.355817948 Joules. Joules is a heat measurement

http://www.unitconversion.org/energy/joules-to-foot-pounds-conversion.html

Conservation of Momentum


http://www.glenbrook.k12.il.us/gbssci/Phys/Class/momentum/u4l2b.html

Once again, retained energy is only part of the equation. What happens with the .22-250 is there is a very high transference of bullet energy to the prairie dog while the larger, slower bullet passes through will a lower rate of transference.



Kinetic Energy (KE) is defined as a function of mass (m) and velocity (v) thusly:
KE=1/2 m * v * v

The standard metric unit of measurement for kinetic energy is the Joule, which is defined in terms of mass (kg), meters (m) and seconds (s) thusly:
1 Joule = 1 kg * ((m * m)/(s * s))

In practical terms, a Joule is the work done by a force of one Newton through a distance of one meter.


But your argument is self-defeating � you cannot have momentum without energy and vice versa.

I think it's important to define the energy of a bullet as primarily kinetic energy, which is the ability to do work due to the bullet's motion.

jwp,

You definitely have a lot of this ironed out, but one thing you said needs correction.

If we have a car doing 60 mph, and a pedestrian who is standing motionless, we can say that the car has quite a bit of kinetic energy, while the pedestrian has none. In a collision, momentum is conserved in that none is dissipated, wasted, or lost. But there is often a kinetic energy transfer, and in this case, there definitely would be. After the collision, the car is slowed down a little (decreasing its kinetic energy), and the person is going a lot faster than he was before (from motionless or flying through the air), and therefore his kinetic energy is increased. So, in this case, there was a kinetic energy transfer from the car to the pedestrian.

It is true that some of the kinetic energy of a bullet is converted into thermal energy, but there most of it is converted into mechanical energy in the deformation of the bullet and the change in position, or "relocation" of animal parts.

Some quotes from a physics professor out of his text book:

"When a force acts upon an object to cause a displacement of the object, it is said that work was done upon the object."

"When the work is done upon the object, that object gains energy. The energy acquired by the objects upon which work is done is known as mechanical energy."
http://www.glenbrook.k12.il.us/gbssci/phys/Class/energy/u5l1d.html

A Joule is simply the unit of energy, which can describe a quantity of any type of energy, be it thermal, kinetic, electrical, mechanical, potential, gravitational potential, elastic, etc.

That's how I always saw it, the energy provided the ability to do work and that work was the damage inflicted....but I'm defianately no expert so maybe Im wrong.

Also, with regards to the "shock wave" vs. hydraulic pressure issue, here are a couple of quotes:

"When the speed of a source exceeds the speed of sound (v > c) the wave fronts lag behind the source in a cone-shaped region with the source at the vertex. The edge of the cone forms a supersonic wave front with an unusually large amplitude called a "shock wave". When a shock wave reaches an observer a "sonic boom" is heard."
http://hypertextbook.com/physics/waves/shock/

"In physics, oscillation that is propagated from a source. Mechanical waves require a medium through which to travel. Electromagnetic waves do not; they can travel through a vacuum. Waves carry energy but they do not transfer matter. The medium (for example the Earth, for seismic waves) is not permanently displaced by the passage of a wave."
http://encyclopedia.farlex.com/Wave+(physics)

There is no "shock wave" when a bullet hits game, but there is a wave transmitted through the flesh of an animal (or test media, or whatever it hits). This wave is what produces the temporary cavity. By definition, a wave does NOT carry matter, only energy. When energy passes through matter, the matter temporarily displaces, and then returns to its initial position.

The permanent cavity is produced by the mechanical energy of the bullet as applied directly to the flesh and blood, as well as the secondary damage done by the bone fragments, tissue fragments, blood, etc. that contacts other, undamaged tissue. This secondary damage is what jwp refers to as "hydraulic pressure," which is a more accurate term to describe the permanent damage done to an animal than is the term "shock wave."

There can not be a transfer of energy if Newton Laws of Motion are correct and I am betting that they are. When a Que ball hits the 9 ball and the 9 ball races across the table you are witnessing a transfer of momentum, NOT A TRANSFER OF ENERGY/
The faster round produces more hydraulic pressure than the slower round despite nearly the same amount of KE. Hydraulic pressure in the small amount of mass that a Prairie dog has stretches past it's limits of elasticity and rips apart.

Jordan, when calculating energy in a collision it is calculated as Joules and the Joules (which is thermal energy is indeed transfer) but it is momentum and hydraulic pressure that creates the wound channel.

Duncan McPhearson dedicates a whole chapter on why any attempt to quantify Wound Trauma Incapacitation is flawed and wrong. The chapter on Understanding Energy Relationships is an eye opener. Since Duncan has a "Ballistics Model" that is proven to be 100% accurate in predicting penetration and wound channel size, he must know what he is talking about.