What Goes Up Must Come Down.

[pvtmorriscsa]

We were having a discussion last night at work. It revolved around the idea of what happens to a bullet if you shoot it straight up into the air. The thoughts expressed by the majority of my co-workers was that if you shot a bullet straight up into the air, it would come back down with enough force to kill someone.

My only arguement was what I had learned in an NRA certified handgun course I took, in which I was told that pointing a loaded firearm up in the air was safe. The instructors granted that if you were to be hit by such a bullet on it's downward course it would not be pleasant, but that it would have no where near the force of a direct shot.

One of the young punk college students at work started to get all scientific on me, and sadly my knowledge of physics is not up to par. Needless to say my arguements were not very persuasive.

I guess what I am asking is who is right; the college student at work, who maintains that a bullet would fall from the height of it's flight with lethal force, or the NRA instructors in my handgun class, who stated a completely opposite result?

[pvtmorriscsa]

d'oh!

Ballastics! Yikes. Ballistics. If someone could correct the speeling in my heading I would appreciate it.

[scottkursk]

If it goes straight up, it should have less velocity than one shot in an arc. Once it gets to the top, it stalls (stops) and then comes down. So the bulltet would have no higher velocity than one dropped from xthousand feet. It'll have to go through a good bit of acceleration on the way down. The real determinant of how terminal the bullet would be would then be its shape and how much tumble it had.

The flatter the trajectory the higher its velocity. A shot straight up would have the lowest speed but I'd not be willing to be on the receiving end of it. I think that would tend to smart.

The Myth Busters tv show dropped pennies from the height of the Empire State Building and it didn't hurt them, though a bullet is much different and is falling with a higher velocity. and alot greater mass.

[AwakeAndFree]

If it goes straight up, it should have less velocity than one shot in an arc. Once it gets to the top, it stalls (stops) and then comes down. So the bulltet would have no higher velocity than one dropped from xthousand feet. It'll have to go through a good bit of acceleration on the way down. The real determinant of how terminal the bullet would be would then be its shape and how much tumble it had.

The flatter the trajectory the higher its velocity.  A shot straight up would have the lowest speed but I'd not be willing to be on the receiving end of it. I think that would tend to smart.

The Myth Busters tv show dropped pennies from the height of the Empire State Building and it didn't hurt them, though a bullet is much different and is falling with a higher velocity. and alot greater mass.

I'm not a physicist or anything close, but if I'm not mistaken - assuming we ignore the air resistance and focus only on the speed of the bullet and its energy - it will return to earth at the exact same speed it left the barrel of your gun.

Still, the air resistance might slow it down considerably.

[DavidOdden]

We were having a discussion last night at work.  It revolved around the idea of what happens to a bullet if you shoot it straight up into the air.

....

I guess what I am asking is who is right;  the college student at work, who maintains that a bullet would fall from the height of it's flight with lethal force, or the NRA instructors in my handgun class, who stated a completely opposite result?

It would depend on what the bullet is (let's assume lead) and its caliber. As I recall, the answer is that a .22 slug could hurt like hell and a .45 could kill you. Terminal velocity on a bullet is rather different from that of a penny, and people do die frequently in New Orleans, especially on New Years Eve. Terminal velocity is affected by air resistance, unlike muzzle velocity; so it is true that getting directly shot has more force, but having a bullet whack you in the head after falling a thousand feet is not safe.

[Godless Capitalist]

Interesting question ... I agree with the post above.

(erandror: You are correct, but since the air resistance does have a large effect knowing just the muzzle velocity is not that helpful.)

How, though, is this related to Objectivism? Perhaps this area should be renamed "Philosophy of Science."

[DavidOdden]

How, though, is this related to Objectivism? Perhaps this area should be renamed "Philosophy of Science."

Hard to say for sure, but here are two thoughts. First, Objectivism is the "Primacy of Existence" philosophy, meaning that what is primary for us is "what is". Naturally, then, anything about the nature of "what is" is important to Objectivists. Second, the reference to "One of the young punk college students" points to a real problem with academia, that more and more, people get to just make stuff up without relating it to reality. Frankly, I have a policy of disbelieving most claims that people make about physics until I have a concrete reason to believe, because too many times I've seen people make claims about e.g. Newton's Gravitational Law which are false. You will find no end of denunciations of academics by Objectivists, so if it had turned out that bullets and pennies were the same, that would confirm a view articulated by a nontrivial number of Objectivists (but by no means all). Of course the reason why things work out okay for the young punk college student is that it's grounded is a science that has a massive connection to reality. Three cheers for reality!

[DavidV]

The velocity of a tumbling bullet falling straight down would become constant once air resistance fully counteracts the downward acceleration. I don’t see how this could cause something more than a bad bruise, and would be interested to see cases to the contrary.

How, though, is this related to Objectivism? Perhaps this area should be renamed “Philosophy of Science.”

Philosophy is the study of fundamental truths, so I don’t think there can be a body of knowledge called “philosophy of science.” One can and should determine whether scientific methods and conclusions are philosophically sound – hence the existence of this part of the forum.

[Thales]

It all depends upon the terminal velocity of the object.

If a man drops out of a high flying plane, he will likely be killed by the impact. However, if he has a parachuet, he will likely land safely. Iows, his terminal velocity is much slower with the parachuet.

Bullets are aerodynamic, so I'd imagine that their terminal velocity is rather high.

Try this link out: Air Resistance...

The calculation isn't straight forward, and depends on the size and proportions of the object. Then, the force of impact is determined by the rate of change of momentum. A more massive particle will have a larger momentum, at the same velocity.

When airplanes are designed, they are designed using so called Reynold's numbers, which are a measure of the speed of fluid flow around an object, and those numbers are usually determined experimentally.

Now, of course, if there were no atmosphere this is a super easy problem, and Erandror would be right. But, the atmosphere does exist.

[stephen_speicher]

One of the young punk college students at work started to get all scientific on me ...

Yeah, those "young punk college students" are a real pain, always bothering with facts and knowledge.

I guess what I am asking is who is right;  the college student at work, who maintains that a bullet would fall from the height of it's flight with lethal force, or the NRA instructors in my handgun class, who stated a completely opposite result?

There is plenty of literature that documents occasional lethal effects of spent-bullets. Or, just ask any neurosurgeon connected with an emergency ward.

[stephen_speicher]

I'm not a physicist or anything close, but if I'm not mistaken - assuming we ignore the air resistance and focus only on the speed of the bullet and its energy - it will return to earth at the exact same speed it left the barrel of your gun.

That is correct. The height the bullet will reach (neglecting air resistance and assuming a perfectly straight trajectory) is a function of the difference between the initial muzzle velocity multiplied by the time traveled, and one-half of the gravitational constant near the earth multiplied by the time squared [vt - (g/2) t^2]. The bullet will stop in its vertical trajectory at a time when the first function is balanced by the second, i.e., when the initial velocity is fully offset by the effects of gravity. From this you can see that the height the bullet rose was exactly the height necessary to reduce its velocity to zero, so when falling straight down it will travel exactly the distance needed to reach the same velocity with which it started.

Still, the air resistance might slow it down considerably.

Yes, most definitely. It depends upon the bullet size and shape, as well as other dynamic factors, but for typical bullets the terminal velocity could be as little as one-tenth of the initial muzzle velocity.

[stephen_speicher]

... but having a bullet whack you in the head after falling a thousand feet is not safe.

It is not unusal for a typical bullet to reach a height of a mile and more.

[stephen_speicher]

The velocity of a tumbling bullet falling straight down would become constant once air resistance fully counteracts the downward acceleration.  I don’t see how this could cause something more than a bad bruise, and would be interested to see cases to the contrary.

There is plenty of documentation for this. For instance, see A. Hanieh, "Brain Injury From a Spent Bullet Descending Vertically -- Report of 5 Cases, Journal of Neurosurgery, 34 (2), p. 222, 1971.

Philosophy is the study of fundamental truths, so I don’t think there can be a body of knowledge called “philosophy of science.”

There can, and there is. One narrows the area of philosophy that applies. Same thing, for instance, with Philosophy of Law.

[danielshrugged]

I've been studying Galileo lately. Here's his answer:

"It seems to me no exaggeration to say that the speed with which the ball is shot from the musket or cannon may be called [unnatural], for in natural fall through air from some immense height, the speed of the ball--thanks to opposition from the air--will not go on increasing forever. Rather, what will happen is seen in bodies of very little weight falling through no great distance; I mean, a reduction to equable motion, which will occur also in a lead or iron ball after the descent of some thousands of braccia. This bounded terminal speed may be called the maximum that such a heavy body can naturally attain through air, and I deem this speed much smaller than that which can be impressed on the same ball by exploding powder" (Drake 228).

Galileo goes on to describe an experiment that supports this conclusion. Basically, it amounts to shooting vertically downward at a stone pavement from low down and also from very high up. If the first bullet is more badly smashed--as Galileo says it will be--then it shows that the initial speed of a fired bullet is greater than any speed that can be gained through falling.

[pvtmorriscsa]

Yeah, those "young punk college students" are a real pain, always bothering with facts and knowledge. 

This would be the same young punk college student that tried to explain to me that global warming was caused by fossil fuel usage. As he has learned in one of his classes. So you will forgive me if I am a bit cynical about his "facts and knowledge"

[stephen_speicher]

This would be the same young punk college student that tried to explain to me that global warming was caused by fossil fuel usage.  As he has learned in one of his classes.  So you will forgive me if I am a bit cynical about his "facts and knowledge"

No, I do not forgive you.

[AwakeAndFree]

There is plenty of documentation for this. For instance, see A. Hanieh,  "Brain Injury From a Spent Bullet Descending Vertically -- Report of 5 Cases, Journal of Neurosurgery, 34 (2), p. 222, 1971.

This is the single most funny remark I've read on this forum since I joined in. Stephen, you rock!

[stephen_speicher]

This is the single most funny remark I've read on this forum since I joined in. Stephen, you rock!

I must be missing something. Why is this funny?

[AwakeAndFree]

This is the single most funny remark I've read on this forum since I joined in. Stephen, you rock!

I must be missing something. Why is this funny?

Oh, wow. This article is real. I mistakenly assumed that you invented this article as a joke, one which I thought was very good.

It never crossed my mind that when someone asks for case studies, you could really come up so quickly with an article titled "Brain Injury From a Spent Bullet Descending Vertically -- Report of 5 Cases" - This article should not even exist!

Sorry for the misunderstanding.

[stephen_speicher]

Oh, wow. This article is real. I mistakenly assumed that you invented this article as a joke, one which I thought was very good.

Oh. Now I understand. If only you would find my actual jokes to be funny!

It never crossed my mind that when someone asks for case studies, you could really come up so quickly with an article titled "Brain Injury From a Spent Bullet Descending Vertically -- Report of 5 Cases" - This article should not even exist!

I am quite a curious guy, and over the years I investigate all sorts of things that are of interest to me. I now keep them on my computer. I have other references for this too.

Sorry for the misunderstanding.

I'm glad you were entertained.

[Godless Capitalist]

One can and should determine whether scientific methods and conclusions are philosophically sound – hence the existence of this part of the forum.

Agreed, but this seems to be a pure physics question; no philosophical analysis is required. Not that I have anything against such questions; it just seemed odd on this forum.

[Lindin]

I suppose it does matter on the angle it was fired and the actual type of bullet, however it definitely is possible for it to be lethal. Some time ago here in Phoenix, AZ a girl was killed from a falling bullet, and a law was passed (Shannon's law I believe it is called?) which makes it illegal. I thought most places in the U.S. this was an illegal action?

[Godless Capitalist]

My question was intented to be rhetorical; I thought it was fairly obvious that this was not a philosophical question. perhaps i was mistaken ..

Hard to say for sure, but here are two thoughts. First, Objectivism is the "Primacy of Existence" philosophy, meaning that what is primary for us is "what is". Naturally, then, anything about the nature of "what is" is important to Objectivists.

But that would make all of science a branch of philosophy. My understanding was that philosophy (specifically metaphysics) was concerned with the fundamental nature of reality, whereas science was concerned with the specific details. No?

Second, the reference to "One of the young punk college students" points to a real problem with academia, that more and more, people get to just make stuff up without relating it to reality. Frankly, I have a policy of disbelieving most claims that people make about physics until I have a concrete reason to believe, because too many times I've seen people make claims about e.g. Newton's Gravitational Law which are false. You will find no end of denunciations of academics by Objectivists, so if it had turned out that bullets and pennies were the same, that would confirm a view articulated by a nontrivial number of Objectivists (but by no means all). Of course the reason why things work out okay for the young punk college student is that it's grounded is a science that has a massive connection to reality. Three cheers for reality!

Good points, but the question wasn't "Should I blindly accept whatever my punk classmates tell me without verifying it?" Clearly the answer to that is "no."

[DavidOdden]

But that would make all of science a branch of philosophy. My understanding was that philosophy (specifically metaphysics) was concerned with the fundamental nature of reality, whereas science was concerned with the specific details. No?

Science, a.k.a. "natural philosophy", does indeed concern itself with the dirty domain-specific details at a level that pure philosophy tneds to eschew. But let's take epistemology, which isn't metaphysics. The facts regarding color -- from the quantum level details about energy absorption through the chemistry of ink and the biology of human cones, not to mention the psychological aspects of color perception -- are very relevant to the epistemological question of whether you can know anything (such as that there is a red apple on the table).

Rationalist philosophies are much more comfortable divorcing philosophical issues from reality, and are more tolerant of just making stuff up. A philosophy that is grounded in "the nature of reality" has a much harder time being disinterested in the nature of reality. Objectivists in particular should be quite interested in the nature of man because Rand has made some strong assertions about the nature of man. These are statements of fact: so the facts count.

Actually, I have a fundamental gripe with all answers to the bullet question (of those that I've seen). AFAIK, this issue has not been subject to realistic experimental investigation. There are lots of factors such as caliber, powder load, winds, the bullet spinning, the fact that "pointing up" usually isn't exactly "up", etc. As is standard, the "answer from calculation" makes simplifying assumptions, and I don't know what the effect of those supressed variables is. Of course given that shooting bullets up in the air actually does kill people, it's not the sort of experiment that I suggest people engage in willy nilly as a science fair project. But, as a curmudgeonly empiricist, I need strong reasons to believe a computation over an observation. However, do have a policy of not going outdoors in the rowdy parts of New Orleans after 11:00pm on Dec 31.

[stephen_speicher]

Actually, I have a fundamental gripe with all answers to the bullet question (of those that I've seen). AFAIK, this issue has not been subject to realistic experimental investigation. There are lots of factors such as caliber, powder load, winds, the bullet spinning, the fact that "pointing up" usually isn't exactly "up", etc. As is standard, the "answer from calculation" makes simplifying assumptions, and I don't know what the effect of those supressed variables is. Of course given that shooting bullets up in the air actually does kill people, it's not the sort of experiment that I suggest people engage in willy nilly as a science fair project. But, as a curmudgeonly empiricist, I need strong reasons to believe a computation over an observation. However, do have a policy of not going outdoors in the rowdy parts of New Orleans after 11:00pm on Dec 31.

These sort of things were experimented with almost a century ago. The first that I have read about was the United States Army sometime after World War I. Army ordnance could not control the detailed dynamic factors involved, but these were real-world experiments with results that ballpark-matched the terminal velocities yielded by calculations. We are talking about factors of ten in velocity reduction so there is little doubt that theoretical calculations were quite good estimates even though they did not mimic (and, could not do so at that time) the many dynamic factors involved. If you are really interested I am sure that your friendly Government Printing Office can assist in locating these early experiments. I am also sure that subsequent experiments have been done in the intervening eighty years or so.

You can also search through the literature, journals such as the Journal of Trauma, for some more modern experimental tests of aspects of this problem. Regardless, based on published documentation of actual cases, in journals such as the Journal of Neurosurgery and the Journal of Laryngology and Otology, that it is not just New Orleans at certain times of the year that we should fear.