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Hi All, High School physics teacher asked me this question & I had no real answer. If you fired a 22 rifle straight up into the air, at what speed would it return at the end? My first thought was at a speed equal to what it left, but then thought maybe even greater due to the gravitational pull. Would air resistance on the way down slow it some? Must confess - I am clueless. So guys & gals, help me out if you can. Thanks. | ||
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Air resistance will, indeed, limit the return speed. My science is many decades behind but it seems maximum is limited to around 100mph or so. Will someone provide the precise term and speed please. NRA Life Endowment Member | |||
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What velocity was the bullet fired at? What is the bullets BC? Need to know those inorder to start figuring it out. | |||
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In a vacuum it would return at the same speed as it departed (discounting that any sizeable body like the Earth or the moon from which it might be launched will be rotating and drastically complicate the equation.) This assumes that the body from which it is launched is not in near proximity to another gravity source and that the bullet is not launched at or above gravitational escape velocity. In atmosphere, the maximum free-fall velocity will depend on the shape of the projectile and its orientation as it falls. In order to reach maximum velocity it would need to be heavy in front and light in the rear (or have "tail fins") to allow the air stream to orient it in its most streamline position. Fired bullets in free fall tend to fall base-first, generally because that's the way the went up and the base is usually heavier than the nose, so the air tends to keep them in that orientation. As I said, I don't know the typical return velocity, but it would likely exceed 100 mph (146.6 fps). There is a verified anecdote of a .45 ACP fired skyward in a New Year's celebration that on return fell through the sheet metal roof of an airplane hanger, then penetrated the wing skin into the gasoline tank of a single-engine airplane, coming to rest inside the tank. During the subsequent flight, the plane unexpectedly ran out of gas in flight due to the venturi effect of low-pressure air coming over the wing sucking the tank dry through the undiscovered entrance hole. Fortunately, there was another independent fuel tank in the other wing, thus allowing the plane to return safely to Earth and the tale be told. I would suspect that a .45 ACP would need more than 146 fps to penetrate roofing metal and airplane skin -- but can assure you that I have run no tests to make this determination  | |||
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33ft per sec squared. Maybe, I duno. | |||
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Assuming the bullet has traveled high enough, it will not accelerate beyond it's maximum terminal velocity through the atmosphere as it descends back to earth. The size, density, orientation and achieved height do matter. The dynamics of fluid mechanics limit the speed not the predictions of projectile physics. Because the density of air varies with elevation the maximum terminal velocity also varies. In short it does indeed make a difference if you perform this experiment at sea level versus shooting the bullet straight up from a mountaintop. | |||
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The bullet will fall back to earth like a rock dropped from that height. The rate of acceleration will be (32 ft per second per second) Now remember that this equation came from a mathematics book from decades ago when I was still in school and also didn't mean much to me then. I have also heard that falling objects with no form of propulsion will only reach about 120 MPH, but I don't know if this is valid or not. Dennis Life member NRA | |||
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32 feet per second per second with a max velocity of 135 mph. I think. One of Newton's Laws. I don't know which one. Google "Newtons Laws" and you can probably find the formula. Ray Arizona Mountains | |||
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 Terminal velocity at sea level is about 120 miles / hour or 176'/ sec. Now that is what I pulled out of my memory bank. Don't know how accurate that is any more.  rogerOld age is a high price to pay for maturity!!! Some never pay and some pay and never reap the reward. Wisdom comes with age! Sometimes age comes alone.. | |||
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On the return flight the bullet will reach terminal velocity. This is the point where the air resistance on the bullet equals the acceleration due to gravity. Acceleration due to gravity is the -32 fps^2 figure that has been mentioned (-9.81 m/s^2 here in Canada) Don't know what the actual terminal velocity will be. According to Mythbusters (i know not real reliable). bullets returing to Earth don't have enough terminal velocity to kill you. (They tried 9mm, 45 ACP and 30-06, not sure what bullet weights. But i would'nt bet too much on this. In short the correct answer will be a lot less than muzzle velocity but need to know about the aerodynamics of the bullet to find out what it will be. | |||
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That 120 MPH terminal velocity is for a skydiving human in the usual arched position. Objects of different B.C. will have different terminal velocities, and a lead bullet will come down somewhat faster. Don't know how fast a .22 LR bullet might fall; it would depend on whether it remained stabilized nose up, turned over nose down or fell sideways. Or tumbled. Hatcher's Notebook contains some information on old testing of US .30 caliber bullets fired straight up. They can come down fast enough to cause a wound. "A cheerful heart is good medicine." | |||
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TaylorJ, Mythbusters did a TV program on this. I don't recall all the details, but I think they came down slower. Perhaps you can find the program somewhere. | |||
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Thanks to all of you for your help. Many good suggestions, but I don't feel so bad now about my own confusion. Anybody else have any ideas? | |||
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This is as close as you're going to get by someone who can actually calculate it.....here......and the terminal velocity will likely be somewhat less than his 270 fps, as he states due to the possiblity of the bullet tumbling and/or falling base first. xxxxxxxxxx When considering US based operations of guides/outfitters, check and see if they are NRA members. If not, why support someone who doesn't support us? Consider spending your money elsewhere. NEVER, EVER book a hunt with BLAIR WORLDWIDE HUNTING or JEFF BLAIR. I have come to understand that in hunting, the goal is not the goal but the process. | |||
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The answer is whatever is the terminal velocity of the bullet. Objects in free fall in a medium do not continue accelerating. Now, if the bullet is tumbling, that velocity is likely to be quite low. If it falls point first, then it is likely to be higher. The answer of "whatever velocity it is fired at" is incorrect. When the bullet is at it's maximum height, it's velocity is zero. It does not remember anything. Peter. Be without fear in the face of your enemies. Be brave and upright, that God may love thee. Speak the truth always, even if it leads to your death. Safeguard the helpless and do no wrong; | |||
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Absolutely Correct! At this point the bullet performs exactly as if it has been dropped from this height. Please note this is only true if the bullet is fired straight up and there is no horizontal component force contributing to its' motion. That is a different problem. There is NO one terminal velocity for all objects dropping through the atmosphere. Here's an example. Skydivers can speed up or slow down their fall by pulling their arms and legs in or sticking them out. They are in fact changing their drag coefficient when they do this. If terminal velocity was not dependent on the drag force of the object falling, parachutes would not work at all. The skydiver weighs the same whether his chute is open or closed. But he definitely falls at different speeds whether the chute is open or closed. Hopes this helps you understand it a little better. | |||
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I have a question for all you math/physics guys. Does the initial energy propel the bullet high enough to reach terminal velocity on the return trip? | |||
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I wonder if the bullet would remain stable (nose up) due to spin or if the spin would slow down enough by that point to not matter. I wouldn't think it would take long from launch to recovery so I suspect it would still be spinning pretty fast. | |||
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Yes. "A cheerful heart is good medicine." | |||
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I'd suspect you're right. Given that gravity is acting upon said bullet's upward momentum with great force, it isn't acting upon the bullet's rotational velocity with any great significance. Couple that with the fact that most of the bullets mass is located in its base, it will, more likely than not, come home base first. Same could be said about marginally stable bullets too, as gravity is acting primarily on the bullets base, not its nose. Nothing like horizontal flight, is it? | |||
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tell the guy to stand under one and see  i believe that terminal for this case would be 128 MPH | |||
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Parachutists can by wearing tight fitting clothing reach speeds of close to 180mph. Typically speeds in Jump clothing "in a tuck" head first won't exceed 120mph, and wearing typical in a spread eagle posture knees bent in flappy jump clothing can be as slow as 70mph. I've read somewhere that in no case can a small arms projectile exceed 300fps, and that would presume a boat tailed projectile fired straight up with no disturbing crosswinds that would initiate precession (tumble) so that the stabilized projectile would subsequently return to earth tail first still stabilized in it's vertical orientation. As a practical matter even slight perturbatations in flight would initiate a wobble which would then a tumbling gyration and the bullet would then fall to earth much slower Typically as slow as 160fps (110mph) Indirect fire Artillery projectiles can do some weird things if flying through wind shear barriers in flight, I don't believe that bullets won't behave similarly a 22 bullet being somewhat more stable but also somewhat more blunt would return more slowly In other words it'll probably leave a mark and might draw blood, but won't actually be moving fast enough to penetrate anything, unless you are stupid enough to look straight up and have it fly into your eye on it's way down... AD If I provoke you into thinking then I've done my good deed for the day! Those who manage to provoke themselves into other activities have only themselves to blame. *We Band of 45-70er's* 35 year Life Member of the NRA NRA Life Member since 1984 | |||
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The findings on myth busters were the same as you guys have stated. They thought the tumbling bullet was slower in dropping. They figured a bullet fired in an arc would be lethal as it maintained some of it's velocity and would remain spinning and thus avoid tumbling. When we were young and stupid we shot a 22 straight up and quite awhile later it came back and landed about 5 feet from where we were standing. Sure make a whack when it hit. the chef | |||
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Here is some trivia Speed of sound in a "dive" ne Giant Step by James M. Clash, Forbes Magazine Joe Kittinger is not a household aviation name like Neil Armstrong or Chuck Yeager. But what he did for the U.S. space program is comparable. On Aug. 16, 1960, as research for the then- fledgling U.S. space program, Air Force Captain Joseph Kittinger rode a helium balloon to the edge of space, 102,800 feet above the earth, a feat in itself. Then, wearing just a thin pressure suit and breathing supplemental oxygen, he leaned over the cramped confines of his gondola and jumped into the 110-degree-below- zero, near-vacuum of space. Within seconds his body accelerated to 714 mph in the thin air, breaking the sound barrier. After free- falling for more than four and a half minutes, slowed finally by friction from the heavier air below, he felt his parachute open at 14,000 feet, and he coasted gently down to the New Mexico desert floor. | |||
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Luckyducker Had it correct from the get go .  For everyones info the projectile will NOT fall point first if shot straight up into the air . Ever see a rocket fall straight back to earth after launching . NO !. Once forward momentum ceases gravity air current and friction take over , it will Yaw back toward earth and may even tumble depending on air current circumstances . One last point " terminal Velocity " is not just a sky diving term !. It's a point of physics . Last I checked my log I had 15 Hr.20 minutes Free fall time !. Average free fall jump 65 seconds from 10,500 Ft. Unless making formations stars Ect. Terminal velocity increases with body masses in the center of a star formation . A Vacuum is created there by increasing speed nearer the center . Shoot Straight Know Your Target . ...  | |||
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Something I was well aware of, but an interesting read never the less But also an extreem over the top example Unless your skydiving club has an SR71 you can parachute from... Starting from 10,000 feet like a typical civilian skydiver you are limited by aerodynamic forces. HALO jumpers can reach higher speeds because they jump from higher altitude where the air is thinner and they intentionally work towards a speedy descent. They are also packing equipment that makes them heavier. The current "competetion speed diving" record is something like 300mph, but those guys use specialized equipment for their faster than normal diving speeds. What actually looks like a lot more fun is a HAHO jump, Consider starting off at >25000ft with a parasail AD If I provoke you into thinking then I've done my good deed for the day! Those who manage to provoke themselves into other activities have only themselves to blame. *We Band of 45-70er's* 35 year Life Member of the NRA NRA Life Member since 1984 | |||
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Agreed ; Although the post was about a .22 cal fired straight up and in no way is it going to come even remotely close too 10K Ft. . The speed remains Appx. 120 MPH ; Whom ever posted it will in flick a wound is right about that . I wonder how many stupid people still fire guns up into the air for special occasions or celebrations !. Shoot Straight Know Your Target . ... | |||
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Is the bullet likely to come back at the point from where it was fired? No! Why? (Give this Q a spin) I'd rather be hunting!! | |||
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 two weeks laterVERITAS ODIUM PARIT | |||
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Here is the dope for a falling 30cal. bullet from http://www.loadammo.com/
300 fps works out to 204.5 mph or there abouts, so a falling bullet will out-accelerate a falling human by quite a bit. This is very reasonable if you consider that lead and copper is much denser for it's size than a human which is mostly water. If you compare the Ballistic Coefficient of the 30cal. bullet to the 22cal. bullet you are using for an example, it should give you an idea of the terminal velocity of the falling 22cal. bullet. ******************************************************* For every action, there is an equal and opposite malfunction. | |||
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For those of us that hunt ducks in a busy flyway you know the feeling of "BBs" falling on your head. Not at all damaging but nothing to get in an eye! They retain such little energy that they cannot penetrate even a baseball style cap.....at least they have never done so to me. /////////////////////////////////////////////////////////////////////////// "Socialism is a philosophy of failure, the creed of ignorance, and the gospel of envy, its inherent virtue is the equal sharing of misery." Winston Churchill | |||
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I don't want to start an argument over numbers or FPS or .30 Cal Army experiments . I will how ever disagree with those findings . It has long been agreed upon the furthest distance a projectile fired from a Cartridge weapon would travel had to be aimed at 34 Degrees and a .30 Cal just wouldn't go that far at 90 degrees!. most people assume it's 45 degrees it's NOT !. At 34 degree elevation it goes like this BULLET WEIGHT (GRS.) VELOCITY COEFF.MAX. CALIBER .30 BALL M2 152 2800 .40 3500 1.99 RANGE (YARDS) RANGE (MILES) ) Caliber with miles at the end. Miles Yards .22 LR (SV) 40 1145 .128 1500 .85 .22 LR (HV) 40 1335 .128 1565 .89 .380 ACP 95 970 .08 1089 .62 .45 ACP PISTOL 234 820 .16 1640 .93 .30 CARBINE 111 1970 .179 2200 1.25 .30 BALL M2 152 2800 .40 3500 1.99 .30-40 KRAG 220 2000 .34 4050 2.30 .50 AP M2 718 2840 .84 7275 4.13 Miles Yards In a Pure Vacuum a .30 Cal 150 Gr. would travel 41.5 miles . As we target pluckers & hunters know we don't live in vacuums . Only our wifes would want you to use one !. Shoot Straight know your target . ... One more point to establish . There have been several people KILLED over the years by falling .22 .38, 9MM .45 & Shotgun slugs fired for celebrations when hit on top of the head or had an artery severed !. | |||
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Dr. K, As you point out the calculations are for a shot fired straight up in a VACCUM. Your figures are not. It's not an apples to apples comparison. Yes I know that we don't live in a vaccum but those figures were evidently included to show the relationship between bullet energy and gravity ONLY without the factor of air resistance to bullet travel. BTW the figure quoted is 21.5 miles travel vertically not 41.5 miles travel. Secondly, your figures show horizontal distance only. Those figures don't show the vertical component of bullet travel. When shot straight up ALL of the energy is put into vertial travel so the bullet will rise much higher than an angled shot. Thirdly, I suspect that the Army's conclusion was the the falling round would not be RELIABLY LETHAL. As we all know a BB gun can deliver a fatal injury under just the right circumstances with a lot less than 30 foot pounds of energy. Yes, there have been a number of people killed over the years by falling bullets but I suspect that all of the variables have to be just right. 30 foot pounds of energy in the small space of the profile of a bullet could probably punch a hole in the top of a skull and indeed be fatal. I don't see a lot of discrepancy between what was quoted and the figures that you provided. 300fps is the standard maximum for competition paint ball guns but as we know paint balls are fairly soft and designed to disintegrate upon impact where as bullets are hard, dense and have a lot more mass than a paint ball. Paint ball warriors also wear a lot of padding and protection over all exposed skin to absorb a lot of the impact energy before the projectile gets to the body. ******************************************************* For every action, there is an equal and opposite malfunction. | |||
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The point being the " Furthest Distance " the projectiles will cover is 34 Degrees Period . Not 90 degrees . Gravity remains constant . Unless fired from Mt. Everst down hill at an appropriate angle . Thinner air less resistance projectile would accelerate for a short period of time . All those figures were at 34 degrees vacuum or not . I was not referencing ballistic lethality only the fact they do impart fatalities if circumstances are right . Check NASA'S Thrust weight gravity vector calculations and you'll see a different story . Shoot Straight Know Your Target . ... | |||
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Doc, You and the Army are very likely both right. The quote says that the bullet will rise to a height of 21.5 mi. in a vaccum if fired straight up. You say that in normal atmosphere a bullet will travel 1.99 mi. horizontally if fired at an inclination of 34 degrees. If you fire a bullet at 34 degrees inclination in a vaccum I would suspect that it would go many times farther than 2 miles. ******************************************************* For every action, there is an equal and opposite malfunction. | |||
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Let's see, there's a 9.8 meters per second per second (per second squared), and consideration of the elevation at which the experiment was conducted, and terminal velocity, and drag coeffecient, and the fact that the friction of the air on the bullet will cause the bullet to heat up and expand thus increasing drag and decreasing the bullet's density, and temperature, and special considerations for a vacuum if you're shooting it off of a planet with no atmosphere, and the curving of space time caused by both the earth and the bullet, and the fact that time moves faster for the bullet the further away from the earth the bullet gets (less gravity = faster clock), and the fact that time moves slower for the bullet the faster the bullet goes (more velocity=slower time), and the fact that the bullet gains both mass and energy as it accelerates, and due to quantum mechanics, the very, very remote possibility that two bullets will come down where there was once only one, at least as long as you don't try to observe/measure it, etc., etc. (aint that a kicker) To sum up, I'm glad I'm through with college physics. Also, you can't really know an answer to something like that unless you acquire super human abilities to somehow quantify all variables and a super computer to calculate all of these factors in your problem. However, since you are just in high school, I have two pieces of advice: 1) Don't take anything more advanced than physics for non-science majors in college (or physical science), or you'll spend the remainder of your days fumbling around with ideas like superposition and big bore ballistics. Ultimately, you might become an AR nerd. Take classes that football players take. 2) I would bet that your teacher does not want you to even consider drag etc. if she/he didn't give you that info. Probably just looking for the terminal velocity. Remember that old thought experiment where the guy drops a penny and a bowling ball, and they land at the same time...? Hint; hint. It doesn't matter how fast it went up as long as it went high enough for it to accelerate back down at 9.8m sec/sec long enough to reach its terminal velocity. Godspeed.  "Sometimes nothing can be a pretty cool hand." 470 Heym; 9.3x74r Chapuis, Heym 450/400 on it's way | |||
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I seem to remember that the return velocity for a bullet fired stratigh up is around 300fps. This is from memory. However I do know that a 9mm luger round fired straight up from a submachine gun takes @42 seconds to make the "round trip". DOUBLE RIFLE SHOOTERS SOCIETY | |||
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According to test conducted by the DOD . I'm not a liberty to give the where abouts of any ballistics info that I might know or have . contractual agreement signed my life in blood !. 32/FPS = Appx. Sea Level 22.4 MPH. Mass ,shape Air Density also plays a role in falling objects . How ever 41.5 miles at 34 degrees elevation in a vacuum is what was written in stone , for a 150 grain 2800 FPS .30 Cal round for Maximum distance regardless of direction . When fired straight up or 90 degrees bullet speed bleeds off faster than at lower angles of elevations . It was found to be more effective to fire upon enemy air craft from ground position too 34 degrees elevation or less . Shoot Straight Know Your Target . ... | |||
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FWIW, Newton's second law of motion applies here. Notwithstanding air resistance, any object dropped will accelerate to a maximum speed of 32.174 ft/s2 (acceleration of gravity). Time(s) m/s ft/s m ft 1 9.8 32.2 4.9 16.1 2 19.6 64.3 19.6 64.3 3 29.4 96.5 44.1 144.8 4 39.2 128.7 78.5 257.4 5 49.1 160.9 122.6 402.2 6 58.9 193.0 176.6 579.1 7 68.7 225.2 240.3 788.3 8 78.5 257.4 313.9 1,029.6 9 88.3 289.6 397.3 1,303.0 10 98.1 321.7 490.5 1,608.7 Lou **************** NRA Life Benefactor Member | |||
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My Father once heard a sound on his asbestos garage roof. Some time later he found a .22lr bullet lying on the roof. It had come down at quite an angle and landed nose first. It was not that badly damaged from the impact, indicating not too high a terminal velocity. If I recall, we estimated a 45 degree fall angle. This is not the same as firing a bullet straight up - it might just come down tail first. Apparently, a pistol bullet will tumble on the way down. Regards 303Guy | |||
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