What Is This

[44MAG#1]

1/2mass (in pounds) X velocity squared / 32.1740 equals what?
Or: velocity squared / 450436 X mass (in grains) equals what?

Is the Kinetic energy of a bullet listed as "Foot Pounds of Energy" or is it some exotic equation

Lets use a 240 gr bullet at 1180 fps. (Remington website on the 44 Mag).

!st equation: .017142857X1392400/32.1740=741.89 foot pounds energy
2nd equation: 1392400/450436X240=741.89

Can we get to a confirmed (by several sources) kinetic energry of the said bullet at said velocity by the equation: 1/2*m*V^2 and nothing else in the equation?
I say no but if I am wrong I want to see it.

[btroj]

That is how you calculate KE.

The real key is deciding what that really tells you!

[44MAG#1]

"That is how you calculate KE.

Which one tells the kinetic energy? The first 2 or the 3rd example?

"The real key is deciding what that really tells you! "
It tells the kinetic energy. In Foot Pounds.
I am asking about the equation/equations and nothing more.

[Iron Mike Golf]

The confusion comes from the fact that weight and mass are not the same. See:
http://www.colorado.edu/physics/phys3070/phys3070_sp06/energy.htm

To calculate kinetic energy, you need to convert weight to mass. Near the surface of the earth, you divide by 1 G (the accelleration of gravity), which is about 32.174 feet/sec/sec.

If you use units of measure other than weight in lbs and velocity in feet/sec, you have to do more conversion. The second formula converts grains to lbs and also takes care of multiplying by 1/2 all in one number.

[44MAG#1]

I assume that most know mass is not NECESSARILY the same as weight unless it is being judged by the same circumstances.
I know a pound of lead weighs a pound here on earth but weighs less in outer space but still has the same mass
This has to do with here on earth dealing with ballistics and is a simple question not a trick question and not asking the difference of mass and weight here or on the moon or some distant planet or any of the other complicated associations one may wonder about but is dealing with figuring foot pounds of energy as most of us use or are use to in our daily lives.

[rexherring]

I skip the math and use this.

http://www.reloadammo.com/footpound2.htm

[44MAG#1]

I guess no one can answer my question.
Thanks anyway.

[roverboy]

Here's how I figure bullet/boolit energy. Velocity squared in fps x bullet weight in grains divided by 450240. For example- if you have a .30-06 load with a 150 gr. bullet at 2850 fps.
2850x2850=8122500 x 150 =1218375000 divided by 450240 = 2706.05677 or just 2706 fps.
Thats just the way I do it.

[Dan Cash]

I guess no one can answer my question.
Thanks anyway.

Looks like you are pole vaulting over mouse dropings. If you follow the answers, especially the one linking you to the University of Colorado, the guys have answered your question(s) several times.

[44MAG#1]

"Looks like you are pole vaulting over mouse dropings. If you follow the answers, especially the one linking you to the University of Colorado, the guys have answered your question(s) several times. "
Yes and that toothpick is hard to hold on to. I am not pole vaulting over anything. Using the UC link then the kinetic enery of the load I mentioned is 23869.71. That is a very powerful load alright. We don't need the 700 Niro Express then.
Now lets get back to what I asked. Can one arrive at the 741.89 foot pounds energy using this equation: 1/2*m*V^2 ? Either one can or one can't. Which is it?

[theperfessor]

Yes, that is the proper equation. you just have to put the variables in the same dimensions by putting in the proper conversion factors.

Start with your basic equation: KE = 1/2*m*V^2

Now remember that mass = Weight/acceleration due to gravity, or m = W/g

Substitute W/g for m into the KE equation:

KE = (1/2)(W/g)V^2

Now, do a dimensional analysis, let's put in common units:

KE = (1/2)[(lbf)/(ft/s^2)](ft^2/s^2)

Cancel out the s^2 in the g term and the s^2 in the V term, and the ft in the g term and one of the ft in the ft^2 of the V term, and you're left with this:

KE = 1/2 ft-lb

The problem is, bullets aren't weighed in pounds, and that weight depends on being weighed on earth where standard gravity constant is about 32.17 ft/s^2. The strange numerical constants you see in various canned equations are nothing more than conversion factors to account for the different units that various variables are measured with.

So can you figure KE with the equation you list? Absolutely.

But everything has to be in consistent units!

[theperfessor]

Let's calculate the KE of a 240 gr bullet at 1180 ft/s.

First convert the bullet weight from grs to lbs. There are 7000 grs in 1 lb, so:

240 grs * (1 lb/7000 grs) = .03429 lb

Now put it in the KE equation:

KE = (1/2)[(.03429 lb)/32.17 ft/s^2)](1180 ft/s)^2

Remember to square the velocity, both the numerical value (1180) and the units (ft/s).

KE = (1/2)[(.03429 lb)/(32.17 ft/s^2)](1180^2 ft^2/s^2)

KE = (1/2)[(.03429 lb)/32.17 ft/s^2)](1,392,400 ft^2/s^2)

Do the right unit cancellation and you end up with this:

KE = 742 ft-lb

[olafhardt]

Actually, you probally need to study some physics to understand this. I did. It is hard to get it across on the web. Energies,momentum, indexes of effect etc along with a host of other things we can calculate don't really tell us much about our guns. I have run through several " knockout" formulas that have shown a thrown softball more lethal than a .458 win. Drinking a warm cup of coffee applies more energy to your throat than a 30-06. If you want to know what your gun will do, shoot it and evaluate the results. This actually tells you what your gun DID, and only indicates what it might do in the future.

[btroj]

The perfesser is dead on.

Both equations in the OP are right, they just show how conversions make it look different.

I have gotten lazy and don't call ate energy any more, I just use a website with a ballistics calculator and let the electrons do the heavy lifting.

[44man]

In the end energy figures do not kill. Bullet/boolit performance does the work. Loading to the highest you can get does not make the gun, any gun, kill better.
Once you understand a .45 flintlock can put deer on the ground faster then a 7mm mag, you will start to grasp the concept.
Toss energy figures very far, they mean nothing.

[44MAG#1]

No one said energy proved anything. I was asking if the correct energy could be arrived at with this equation: 1/2massXvel^2 with nothing else added or taken away from it. It can't as one needs to divide the answer by 32.1740 to get the foot pound energy.
The equation should be 1/2 mass X vel^2 / 32.1740 to get the original 741.89 foot punds energy.
Without dividing the answer of the first part of the equation by 32.1740 it is not going to produce the correct answer.
MASS AS DEALING WITH BULLTS IS IN GRAINS WHICH IS A UNIT OF WEIGHT ASSOCIATED WITH POUNDS. 7000 GR TO A POUND. We all know that.

[btroj]

Mass is NOT a unit of weight. grams are a measure of mass, pounds are a measure of weight. Grains a re techincally a measure of weight.

Mass is a measure of how much of someing you have.

Weight is a force. Weight is mass times the acceleration of gravity. That is why that pesky 32 is in there.

This is all basic physics.

Use the formulas as you have them, the 32 factor is critical.

This is also a great example of why I use online calculators, I can put in bullet WEIGHT in grains and velocity in fps and get a correct answer every time.

[44MAG#1]

Now you get why I asked the question in the first place.
The 32.1740 IS critical in the equation.

[theperfessor]

Bullets are specified by weight. But the kinetic energy equation requires that mass be used, so to convert weight to mass you have this relationship:

W = mg, or rewrite it as m = W/g

Put that in for mass and you have KE = 1/2(W/g) V^2

The g is the 32.17 ft/s^2 required to convert weight measured at the Earth's surface to mass.

If you keep using weight where mass is required you will always get the wrong answer.

[44MAG#1]

That KE = 1/2(W/g) V^2
is not the equation given.
Given 1/2massXV^2.

[btroj]

Now you get why I asked the question in the first place.
The 32.1740 IS critical in the equation.

Yes it is because we WEIGH our bullets, we need to calculate the MASS of them to calculate energy.

Common mistake for people to ink of weight and mass as being the same.

[theperfessor]

Yes that's what you gave. And after converting the weight into mass by using W/g that is the equation that was used. W/g is equivalent to mass. One way or another you have to convert weight to mass to use the KE equation you presented. And grains is a weight term, not a mass term. It always has to be converted to mass. If you knew the mass of the bullet you could plug it right in. But that would mean you've already used g = 32.17 ft/s^2 somewhere to find that mass.

[theperfessor]

By the way, the mass of a 240 gr bullet is 0.0010658 lb-s^2/ft. I'll stay away from slugs, which is the standard mass unit in the English system.

[MtGun44]

Must use Mass in KE, NOT weight, they are not the same.

If you have not had any physics, it is common to think mass and weight are
the same thing, and they are not and the calculation requires MASS units.

Conversion from weight units to mass units requires you calculate based on
the gravitational field you are in. Here on earth it is 1 G. On the space station
it is something like one millionth of a G or less. MASS is the same in both places,
WEIGHT is nearly zero on space station due to low gravity.

Weight is the result of a mass being acted on by gravity. Mass is an amount of
matter, weight is a force.

Read the perfesser's posts.

Bill

[btroj]

Mass is weight divided by the acceleration of gravity.

Again, mass and weight ARE NOT the same.

Mass is mass, weight is a force. Force equal mass time acceleration. The acceleration in weight is gravity.

KE is 1/2 mass x velocity squared.

Since mass is weight / gravity you end up with the equation the Perfesser gave you.

[Mooseman]

Mass is weight divided by the acceleration of gravity.

Again, mass and weight ARE NOT the same.

Mass is mass, weight is a force. Force equal mass time acceleration. The acceleration in weight is gravity.

KE is 1/2 mass x velocity squared.

Since mass is weight / gravity you end up with the equation the Perfesser gave you.

Excuse Me , but Mass is expressed as weight.
Weight definition is
1.
the amount or quantity of heaviness or mass; amount a thing weighs.
2.
Physics . the force that gravitation exerts upon a body, equal to the mass of the body times the local acceleration of gravity: commonly taken, in a region of constant gravitational acceleration, as a measure of mass.
3.
a system of units for expressing heaviness or mass: avoirdupois weight.
4.
a unit of heaviness or mass: The pound is a common weight in English-speaking countries.
5.
a body of determinate mass, as of metal, for using on a balance or scale in weighing objects, substances, etc.
Mass is normally expressed in Kilograms , etc.

[theperfessor]

Don't know where you got those definitions, but the only one that matters in a scientific discussion is definition #2. The rest are common misinterpretations of the relationship between weight and mass and are quite honestly WRONG. The fact that weight and mass are used interchangeably by misinformed people who don't understand the technical distinctions between them doesn't matter. Weight and mass are expressed in different units and describe different but interrelated properties.

And calculating kinetic energy requires the use of mass, not weight.

[theperfessor]

Actually, 5 is correct, but 1, 2, and 4 are seriously wrong.

It might be noted that the SI (old metric) system is a mass based system, vs the weight based English system. This is another source of confusion, since grams is a measure of mass, and Newtons is a measure of force or weight. The fact that this has also been corrupted by people using grams as a weight is also WRONG and can only happen in a constant gravity environment.

[Matthew 25]

theperfessor is actually the sharpest knife in the drawer.

[Mooseman]

So...is "kilograms-force" weight or Mass ?

[btroj]

Kilograms are technically a mass unit.

Mass is a measure of how much of something we have. Weight is a measure of the downward force that mass of stuff has due to gravity.

This is an area that commonly confuses people because the term mass is so rarely used outside the science world.

The sticky part in the KE equation is that unless we factor in the gravity number we get a result that is way too hight.

[felix]

It's all funky monkey business when you really get down to it. All measurements are. They are all descriptions of what is what so various men (scientists, engineers, technicians) can be employed to reshape (objects, thoughts) into something else (objects, thoughts) more satisfying. ... felix

[44MAG#1]

How much does the mass of matter of a 240 gr bullet weigh on earth?
If it is propelled at 1180 fps how much foot pounds of energy does it have.
If the same bullet is on Jupiter with the same mass of matter with the weight it has on Jupiter and it is propelled 1180 fps how much foot pounds of energy does it have?
Since mass is not weight and weight is not mass foot pounds of energy doesn't exist.
Since mass is not weight and weight is not mass momentum doesn't exist.
I see now.

[theperfessor]

Mass doesn't "weigh" anything. The same bullet shot at the same velocity has the same kinetic energy no matter where it is. As others have said repeatedly, mass is how much MATTER there is of an object. Moving that object to a place that has a different gravity field doesn't change how much matter it has.

Weight or force is what you get when gravity or any other form of acceleration acts on the mass of an object. Without gravity or acceleration there is no weight. There is still mass.

And since kinetic energy is an inertial property mass, not weight, has to be used in calculating it. Thus the conversion needed to convert weight to mass.

Honestly, it is pretty simple to understand. And it is SCIENCE not OPINION. The relationship between weight and mass is a fundamental relationship in Physics. This is just about topic number one in any basic physics class from early high school onward.

Guys, I've spent more than half my total life (and 3/4 of my working life) trying to make difficult topics in science and engineering easy to understand by people who honestly want to learn. I've been cited for excellence in instruction and get very good student reviews. I paid my own way through a small state school and while a student I tried to learn as much as I could from the people that knew the truth and were willing to share that with others. I've never thought of myself as being special, as many other people who learned their lessons in school know as much or more than I do about many things. Virtually everyone I work with is smarter than I am about something. And I love it, because I get the chance to learn something new virtually very day.

Over the years I've found out that most people who want to learn and who will get rid of the wrong things they think they know about science can do pretty well. Those that keep confusing various properties and their relationships can never advance. I've tried to shed a little light here on a basically simple subject, but it's hard on a forum to help people that apparently have never had a basic physics class or don't understand basic symbolic algebra to understand even this topic.

I've received numerous pms claiming that I'm being "tricky" or using "science" instead of who-knows-what to answer the OPs question. I'm also apparently guilty of having a fancy degree (really? I'd like to know where it is?) and other thing too numerous to mention.

In all of this I have not made a single personal attack or insult. I have not accused anybody of anything. I have tried to explain a simple concept in simple terms. At this point I can do no more. The truth is there, several posters and myself have put it out there.

I'm finished trying to educate those who choose not to learn. To be ignorant is not a sin, we are all ignorant of many things. To choose not to learn is a sin, the biggest one that any creature with a brain can make. To those I would say: change your attitude and take an algebra and physics class.

I'm done with this discussion.

[TAMU74]

A+ Perfessor. I spent many years in the front of a high school physics classroom and found that trying to get the students to accept scientific meaning of the terms that they had heard misused and misused themselves for so long to be one of the most difficult parts of the the learning process,sadly some of them never did. One thing that helped me was the fact that mass is not only a measure of the amount of matter an item is made up of but also a measure of its inertia or resistance to any change in it state of motion. A confounding factor was that to measure mass we commonly use gravitational balances to measure mass and until I began to demonstrate and teach the use of inertial balances did they begin to grasp the difference.

[44MAG#1]

Since a bullet is comprised of matter it has mass
Since mass has no "weight" then it cannot have foot pounds of energy.
Since mass is matter and mass has no weight matter has no "weight" so it cannot have foot pounds energy.
I see now.
This is then a study of terms. Right?
If mass of matter has no weigh how do we quantify it? How do we know it exists since it has no weight. If it has NO weight it therefore cannot exist.
Now how does a bullet punch a hole in paper or kill an animal if it a "mass" of "matter" since it has no weight it cannot have any form of power because to have a form of power it has to have weight to produce momentum or foot pounds of energy or even Taylor Knock Out Value because that bullet has to weigh some quanitive value.
Or does the "mass of "matter of said bullet have a weight and it is 240 grains convereted to pounds which is .03285714 pounds but we can only figure half of that mass of matter (that has no weight though) which is ..017142857 pounds to use in an equation like this
.017142857X1392400/32.1740=741.89 fpe (which doesn't exist because we all know a mass of matter has no weight).

[44MAG#1]

What this has really come down to is I used the wrong term. Mass. I should have said 1/2 bullet weight in pounds but I stupidly used mass.
The question I was asking was in the equation 1/2massXV^2 was that the divsor 32.1740 wasn't included to reduce the answer of the first part of the equation to foot pounds energy.
It was then jumped on by the local brains when I feel most knew what I was talking about when I used 1/2 mass because a bullet is a mass of matter, has a density, has a volumn and has a weight on earth due to the gravity pulling on it of 240 grains. Just the same as if we step on a scale we weigh a certain amount. We are a mass of matter with a density and we take up space so we have a volumn.
I did not think this would be a science class of mass vs matter vs weight vs volumn vs the dark of the moon or how we part our hair if we have hair where the part suppose to be.
Due to me using the wrong term as most of us do on occassion just like misspelling a word or words as most on here, including me unless we use spell check, this has been dragged over the coals just to satisfy the few.
I will remember this escapade in the future.
Thanks to all who have schooled me in mass and matter. I now know that using the exact true term of anything is so important because most don't have any common sense enough to figure out what I meant using the term mass.
I remember reading the late Elmer Keith writing about revolvers and using the turm bolt for cylinder stop and the cylinder stop notches as bolt cuts. Is that a misnomer for them or are they cylinder stops and cylinder stop notches. Other thing can be brought up that the wrong term is used for.
It would look like most on here would be offended that a "FEW" on here thought most of you didn't have enough common sense to know what I meant. I bet it is hard to carry on a live conversation with "The Few" because of the fear of being corrected on every mis speak and use of the improper term. I be t it is a harrowing experience to say the least.
Me with my my Tennesse Hillbilly stupidity I would be so fearful i couldn't speak.
Thanks again to all the instructors on here.

[btroj]

The mass of the bullet on earth and Jupiter is the same, the weight is not.

The astronauts on the moon could leap farther and higher due to reduced gravity, their weight was lower.

Don't feel bad, I have a BS in Chemistry and still kept forgetting about th 32 factor for gravity for years. Drove me nuts and I should ace known better.

[nodda duma]

Tennessee .. Hell man, I'm a hillbilly from Arkansas and while I might not be able to tell the difference between my cousins, I know the difference between mass and weight ;)

All you gotta do is use your noggin for more than just an eyeball holder and a couple air holes! That and read the answer theperfesser gave ;)

[John Ross]

OP, to answer what I think was your original question, the formula 1/2 mass times velocity squared is correct for calculating energy. Your apparent confusion about the two "different" equations comes from the fact that conversion constants need to be used to get the units in the desired form. Post #11 explained this in detail; here's the Cliff's Notes version:

KE=1/2 MV^2 is a simple-looking equation, yet the calculations we see for energy look a lot more complicated. This is true for every real-life math problem. The forward velocity of a car is engine speed times tire circumference divided by overall gear ratio. But the engine speed is revolutions per MINUTE and the tire circumference is in INCHES, but we want our answer in MILES PER HOUR, so we have to use conversion constants to get our answer expressed in the units we want.

The whole mass and weight thing was a bit of a detour from what (I think) you were asking.

[felix]

Communication is the separator between man and the rest of the animals. Different men have different communication skills, as intended by the Creator. Math is a man-made language specific to those folks who HAVE to communicate to manufacture anything. It's that simple. ... felix

[MtGun44]

Words mean things. As soon as you get past a discussion of fuzzy social issues into
any sort of technical issue, you must use the correct word or communication will
be impaired or fail.

You getting snippy about us pointing out that you were using the wrong word is
not a useful attitude for friendly, useful TECHNICAL communication. Precision in
use of terminology is absolutely critical in this hobby.

I'm with the perfesser - done with this foolishness and waste of time.

Bill

[err.gray]

Uhhh...Would you like fries with that?

[44MAG#1]

I want thank the perfesser, whatever that is, MtGun44 for the setting me straight of my intellectual inability to communicate with the people on this fine forum.

I want to say I am sorry for using the word mass and mass was the incorrect term.
Now I am going to start working on other terms I use that may be wrong or inaccurate to some degree.
Since no one knew what I meant I am sorry.
Lets let this fade into oblivion and hope I will never use the wrong term again that will offend the perfesser and MTGun44
It is good that there are a few people like me in the world because that gives some the ability to educate and to point out others shortcomings.
It would be difficult to show off intellegence if all were on the same level of education and knew the same things to the same degree.
Just like shooting. If all were the great shots like some are the great ones wouldn't be able to show off their great groups to the paltry few.
Just be glad there are people like me to zero in on.

[waksupi]

I prefer to see correct terms used, so as to not confuse anyone looking at a thread at a later date.

[btroj]

I don't see it as "zeroing in" on a person. I would far rather work to bring your knowledge up to my level than allow you to unknowingly use a term incorrectly.

I am happy that we cpgot pur math problem figured out for you. Like I said, I know better and I still let that dang 32 bug me for years.

You were smart enough to know soemthing was bugging you and it needed answering. I am glad you came to a site where you not only learned how to solve the problem but WHY it worked the way it did. Too often we are given an answer but not given the why. I need to know the why.

[44MAG#1]

btroj:
I am glad you are working to bring my uneducated self up to your knowledge. I will be able to go to the range in the morning and have the assurance that you guys have my back.
Now if I could just get you guys to teach me the fine art of shooting I would be happier still.

[waksupi]

btroj:
I am glad you are working to bring my uneducated self up to your knowledge. I will be able to go to the range in the morning and have the assurance that you guys have my back.
Now if I could just get you guys to teach me the fine art of shooting I would be happier still.

When you have people trying to be helpful, and you give wiseacre remarks back, I expect you will not receive many answers in the future. You were unintentionally wrong in your statement, and the statement was corrected. Happens to a lot (most) of us. You would have been better served with a "thank you", and maybe at this point, an apology.