O/T for you science buffs

A little background first: In posts below, I've run ballistics formulas and 32 ft./sec./sec. formulas in a spreadsheet and found the normal ballistics you get from www.remington.com give you 2500 to 3500 fps out of the muzzle with 2500 to 4000 ft. lbs. of "torque" on a 40 to 200 grain round that has .21 to .50 drag coefficient from a 24" barrel. It goes up a mile or two, gets to 0mph and falls at 32 ft./sec/sec. Usually the result is 200 to 300 fps when it hits. If you make goofy assumptions like no atmosphere but still 1G earth gravity and set drag coefficent to 0, you can get bullets flying up 20 or 30 miles - but they still land 100 or 200 fps short of 0 atmosphere muzzle velocity speed. If you go to the moon, they fly real well at .2G moon gravity, but you're bit on the backside as .2G = .2*32ft/sec/sec. You need more distance going up, or in other words, a more powerful gun. Then I remembered something I'd read about Gerald Bull and super guns, and realized it can be, and actually has been done. The method even has something to do with old tractors.

Think of the bullet as a tractor piston, and the gun barrel as a tractor cylinder. The tractor has piston rings, but they're missing in the gun. Bull figured out a few things, one of them was adding piston rings to the gun. He took a device that sealed to the barrel and placed a round about 80% the size of the bore inside it. The device is formed in two parts, so it falls away after the round has left the muzzle, while the light sub caliber round keeps going. Guys who hunt with .50 cal black powder can find basically the same thing in their sabot rounds. Next trick was that with those "piston rings", the bullet doesn't need to be shaped to seal to the barrel. Heck with boattail rounds, he shaped his bullet to look something like a football. Instead of the .2 to .5 aerodynamic drag you're used to seeing in ballistics charts (or cars and trucks) this thing has a coefficient approaching .1. In other words it slips throught he air with the greatest of ease. Last trick was increasing torque. A longer stroke engine increases torque, right? Same trick with a long barrel gun. The same .44 caliber round has more punch when fired from a Remington rifle than it does from a Colt pistol. Reason is that you use more of the explosion energy to push the round, and less of it escapes at the muzzle.

Enter Uncle Sam who's looking for a cheap way to get extra supplies up to astronauts. They hire Bull to design a super gun which would go up 100 miles then fire a small rocket to reach low orbit. They take two 16 inch naval guns, weld them together, and get a barrel about 100 feet long. Ship it to Arizona, and point it straight up. Insert the football shaped round they call a Martlett inside the piston rings or sabot, and pull the trigger. In Nov. 1966, they got a 185 lb Martlett to an altitude of 111 miles. It falls at least 90 miles at 32 ft/sec/sec before it encounters much atmosphere - and ends up hitting faster than when it left the barrel.

Don't try this at home, as you're likely to end up demolishing your house. And don't be Gerald Bull, as he got assassinated for hiring out to a guy named Hussein. The point is something most tractor guys already suspect; you can do most anything with a bit more power.

Rod

The original question was:

"if I was to point a gun straight up in the air and fire it, the bullet would go up, and then fall back to the ground, reaching the same speed as when it left the barrel. Is this fact or fiction?."

That's why the muzzle velocity, or the speed it was traveling when it left the barrel is important. Gotta answer the question - so you have to know the original velocity to compare it to the final velocity when it hits the dirt.

A ballistics table rates the speed, force, and air friction coefficient for a particular round. The force, energy, punch, of the round is rated in foot/pounds. Torque is rated in foot pounds. As one of the themes was to draw some relation to a tractor engine -- seemed a bit interesting to throw in "torque" in a tongue in cheek sort of way instead of using the words force, energy, punch, etc. over and over ad nauseam. Yes, torque is properly a turning force - but it's easily translated to lifting force as the common currency is foot/pounds.

The energy number in foot pounds already assumes a 1G gravity by telling you a 2000 ft/lb round can lift 1 pound 2000 feet, half pound 4000 feet, quarter pound 8000 feet, and so on - all ratings done on earth - and with a given amount of powder charge in the round. So the gravity correction is basiclly "built-in" with differences that are negligible. The wind resistance or drag coefficient get substantial with various shapes of bullets, though.

Think that covers all your questions, yes?

Rod

As for the bullet attaining muzzle velocity, let's assume a muzzle velocity of 1,500 fps, x 60(seconds), x 60(minutes), divided by 5280(feet per mile) = 1,022.72 mph. (That distance is not going to be attained because of air resistance.)

I VERY seriously doubt that ANYTHING falling from ANY height within the Earth's atmosphere is going to attain that sort of speed. If my calcs are correct -- and I'm NO maths genius -- terminal velocity, 120 mph, translates to 176 fps, just a little short of the above assumed 1,500 fps muzzle velocity.

Anybody got any corrections here? I'm always open to learning.

You have a wonderful day. Best wishes. Deas Plant.

As an entertaining sidebar, this claim of bullets falling at muzzle velocity is used by gun control groups who insist thousands of people die every year from falling bullets.

The reality is the bullets reach a terminal velocity that is about the same as a rain drops or a hail stones. People don't die from falling bullets.

Regards, RAB

LOL Larry

Things accelerate as they fall, until they reach their maximum speed limited by air friction.

If you drop a penny off of the empire state building, it can kill a person on the ground.

What happens when you fire a projectile upwards is that the kinetic energy of the projectile is converted into potential energy. When there's no more kinetic energy left, the projectile stops, then falls to earth. As it falls, the potential energy is converted back to kinetic energy. In a vacuum, you 100 percent of the energy you started out with. On earth, a huge amount of energy is lost to air resistance, so the projectile will fall to earth much slower than its original velocity.

Duck!

ok here's one for your teacher, if you are in a car traveling the speed of light at night and you turn on the head lights, can you see in front of you? if you look in the rear view mirrow, can you see behind you?

Consider this: Two Apollo space craft, both in the vacuum of space. Both have just slingshoted around the moon. One fires a rocket (pulled the trigger on the rifle) the other does not, and just relies upon Earth's gravity for its return. Which one gets home first? The one that fired the rocket, of course. Both have Earth's gravity pulling them, both are in a vacuum; but the rocket powered one has used Newton's 3rd -- every action results in an equal and opposite reaction --and gets home first. End of story. The speed of the rifle bullet leaving the tube against gravity is about 10 times greater than the speed of the bullet falling to Earth, propelled only by gravity. That's real simple.

Also consider this: Cmdr Dave Scott, on the moon, 1971. Drops a hammer and a falcon feather at the same time. Near perfect vacuum. The feather hits a tad later than the hammer -- greater mass in the hammer. Galileo was right -- 400 years earlier.

Speed of light. We leave Newton and enter Einstein territory. If E=MC squared, then at the speed of light, you're pure energy anyway, and don't see a thing. Assuming you're not pure energy, you neurons don't run faster than light speed anyway, so you don't notice any difference in anything you see from one moment to another, as everything is constant.

the Apollo example has little to do with the bullet example. but, i agree that for every action there is an equal but opposite reaction. in the Apollo example the acceleration of gravity added to the acceleration of the bullet in the opposite direction will increase the average velocity of the capsule.

in the students question, the velocity of the speeding bullet is decelerated by gravity to zero and then accelerated by gravity back to it's high velocity. in the bullet example V initial (after leaving the barrel) will be decelerated to V final (0) by earths gravity (no air ok?) at that time gravity (the same gravity that slowed the bullet) will pull the bullet back to earth. this time V initial will be 0 and v final will be the high velocity. since their is no air friction, the bullet cannot loose energy in any way, only trade kinetic energy for potential energy and then back to kinetic. the time up will be equal to time down, the gravity will be the same the v initial (up) and v final (down) will be the same. the balance of the two formulas is the same. vfinal squared = vinital squared + 2as a = gravitational acceleration (32.2 ft/sec/sec or 9.81m/sec/sec) s = distance traveled. there is no qualifing the formula as to if it is used with gravity or against gravity, only the sign of a changes (either positive or negative)

the feather and hammer thing. the greater mass of the hammer also means a slower initial acceleration by gravity while the feathers lower mass means a faster initial acceleration. the only difference is final force applied by the two objects. the time for the fall is the same. you are correct, in that Galileo observed this experiment, you are however incorrect in that his observation showed both to hit at the same time. (legend of tower of Pisa) he used two spherical objects of the same size but of vastly different weights so that the present air would effect both equally. the formula for time of a fall such as this is: time= the square root of twice the distance dropped divided by the gravity constant. you will notice that neither weight nor mass is associated with the formula. I cannot account for the experiment you mentioned, but will look into it.

if you will remember your scientific history, you will remember that the concept that was the basis of reletativity was a passenger on a train that accelerated to the speed of light. the formula e=mc squared actually uses the speed of light as a quantitative value not qualitative statement. It was the basis of Einstein’s later work, my examples deal with his earlier work. Again I agree with you in that I would not want to go that fast , especially with our roads in Virginia, but again in theory the passenger would both see forward and backward. Speed of light being constant therefore time itself must change as speed changes. if you consider the neurons as also part of the passenger then they are already at the speed of light and any displacement of signals either from the eye to the brain or from the brain to the eye being onlt relative to motion inside the car, not outside.

I know this is tripe to some but it is important to the education of our children. The most complicated events must be simplified and studied before the actual complicated world be explained. that’s why its important to understand bullets in a vacuum before understanding bullets in real world air. By the way, Robert in W. Mi has it correct in that Hatcher did the experiment, for another discussion we could talk about why Hatcher theorized that in a perfect experiment,the bullet would also come back to land on its base not its nose. Man, I love this stuff. and for those that think the deal about doers and teachers, the best acceleration formulas i've ever seen are in The Machiner's Hand Book. you can bet your bottom dollar that machinest that "do" have that book, whether they share their knowledge with a student or not.

No leg pulling involved. The statement on the first post was: "then fall back to the ground, reaching the same speed as when it left the barrel." The descending bullet, like the Apollo with no rocket burn, is propelled by gravity alone. The ascending bullet, like the Apollo with a rocket burn, is propelled by a force far greater than Earth gravity. Vacuum or atmosphere, the ascending bullet initially travels faster than the maximum speed of the descending bullet. Newton's 2nd and 3rd laws hold true. Read down a few posts - I calculated the speed differential between the initial upward velocity and the final downward velocity as about 10:1 using Galileo's basic 32 ft per second per second time relative constant acceleration rate for the downward speed, using 4800 ft as max altitude and holding wind resistance at zero, as in a vacuum.

Galileo was disproving Aristotle in Pisa. Aristotle had said gravity was a differential force relative to weight. Galileo showed that the distance a body has fallen at any instant is proportional to the square of the time spent falling proving that all bodies fall with the same constant acceleration regardless of weight. Galileo's fabled lead and ebony balls actually hit at slightly different times because of Newton's 2nd law that acceleration is inversely proportional to mass.

Move to Einstein and you find a link to the above gravity and mass problems in E=mc* which explains the paradox of how light behaves in relation to gravity and its mass. Light has no "resting mass", but does have motion, and can be bent by gravity, therefore it must have some kind of mass. On your Virginia roads, we've neglected to note that E=mc* dictates that light speed causes an increase in mass. Einstein argued that the laws of physics in a laboratory under uniform gravity are identical to those in a laboratory undergoing an acceleration, and thereby developed the idea of gravitation as spacetime curvature. He found that the gravitational field, like the electric field, should also have mass. Gravity, too, will be a source of gravity; distorted space contributes to its own further distortion.

Einstein reached his new theory of gravitation -- his general theory of relativity - in which gravity is a spacetime distortion. Yet he never did develop a unified theory, as gravity is not integrated with electricity, nor is the weak force and the strong force fully explained. So our children must know that we don't understand how the electricity in our neurons will behave in that lightspeed spaceship - and therefore cannot answer the question. Thanks for picking up on that question I left and giving me the opportunity to talk about what Einstein and Stephen Hawking, et cetera don't know.

vfinal squared = vinital squared + 2as a = gravitational acceleration (32.2 ft/sec/sec or 9.81m/sec/sec) s = distance Do you deny the formula? has nothing to do with weight or mass and is used in a frictionless enviroment

if you would like and to keep others from knowing how pig head people can be we can continue by email.

OK, let's say vertical plane, no air, only gravity. The amount of force in ft/lbs. on exit from the barrel is say >1300 ft/lbs. (no energy expended to clear the air from the barrel), velocity of the round goes to something in the neighborhood of 3000 mph at the barrel, and the max altitude of the round goes to about 11,000 feet in a vacuum, lifting a 55 gram round, working only against earth gravity. From 11,000 ft to 0 feet at 32 ft/sec/sec (the formula is correct) and weight is irrelevant in falling - (but it is relevant in knowing how far up the round can fly given the power of the explosion). I eyeball it at a about 600 mph when it hits the ground. So the answer to the science teacher is you're wrong, we were going faster when we left the tube than when we hit the ground.

Run the numbers and let me know if you come up with something markedly different, or see some flaw in my assumptions.

while i was bushhoging today, i thought about the comment i closed with, and was afraid you would think it was focused at you. i ment it to be inclusive of myself. i glad you seemed to take no notice.

Anyway, the best round I found in the ballistics tables at www.remington.com was the 300 Rem Ultra Mag which by throwing out my ballistics formula and simply using ft/lbs. of torque versus the 180gr. weight of the round gets to almost 31 miles. No good, still over 100 fps short at the ground.

Then I started looking for Mama Deuce 50 cal ballistics, didn't find them, but started thinking of bigger guns. Remember the Paris gun the Germans used in WWI with a 70 mile parabolic range. Then the progressive charge gun they designed to shot in France and hit London. Projected ranged was 140 miles. Then remembered Gerald Bull, and it turns out he actually did it. In Nov. 1966 a ~100 foot long barrel super gun shot a 185lb. Martlett to an altitude of 111 miles. Bingo. It can hit as fast as it left. I take it all back -- it can be done, but not with any ol' rifle you're likely to pull off the rack. I'll do a post about the magic of the Martlett approach at the top.

Sorry for makin' your head hurt. Have a good weekend.

Steve

Pete

Somebody has never read about Galileo dropping balls off the tower of Pisa or Isaac Newton sitting under the apple tree -- and hasn't learned some basics of physics. Gravity works at a constant rate of acceleration, with specific gravity or mass and wind resistance being the only variables at altitudes under ~ 6 miles. A falling body accelerates at 32 ft/sec per second, or slower with wind resistance and lower mass.

Knowing that, we can do the experiment by writing on a napkin. Take your standard issue M16 rifle over to Iraq and fire it straight up at Saddam on a magic carpet. The GI 55 gram FMJ round leaves the tube traveling at 3240 feet per second or 2209 miles per hour with about 1200 ft/lb's of energy at the muzzle and 180 ft/lb's of energy at 3000 feet. As we've missed Saddam so far, the round travels a little under 4485 ft up (180 ft/lbs of energy on 55 grams at 3000 feet spec less wind resistance) before it loses all energy - literally stops for an instant - and then becomes exactly same kind of thing that Galileo dropped from the leaning tower in Pisa. From 0 feet per second at its peak, gravity makes it accelerates at Newton's 32 ft/sec per second until acceleration is neutralized by wind resistance. It works out to a maximum speed of about 307 feet per second, or 210 miles per hour.

Also, think of it backwards. If this "teacher" were right about the bullet - a piece of hale dropped from a cloud at 8000 feet, even with its lower mass, would still hit your head at something over 1,000 mph - and you'd see dead bodies on the sidewalk every time a hale storm rolled through.

I have the book, but it's been many years since i read it!!

Robert

Your teacher never read about USAF Capt. Joe Kittinger who rode a skyhook balloon 102,000 above New Mexico then jumped. He reached a maximum velocity of 625 mph (not quite supersonic), as he fell for nearly a minute before encountering any significant atmosphere.

He opened his chute at around 50,000 feet and walked away smiling when it was all over.

Just my .02 worth.

The 0 atmosphere assumption requires 0 gravity (gravity being the stuff that holds atmosphere), so that assumption is about as valid as the proverbial wings on pigs = flying pigs.

If the round is copper, which has a specific gravity or mass of ~8.5, the effect of the round hitting you would be the roughly equivalent to 8.5 same size drops of rain hitting you in the same place in the same time -or- or 1 rain drop propelled by gale force winds (water having a specific gravity of 1.00 by definition). As I know of few deaths from rain in gales, much less hurricanes -- I think you'd survive, and wouldn't even suffer penetration of your skin.

The moon does have gravity and it does have an atmosphere. The Apollo program identified helium and argon atoms there, and Earth-based observations added sodium and potassium ions to the list in 1988. Promise it's true, look it up.

Only space with zero gravity will never attract an atmosphere -- therefore in any natural, non-artifical, state; the 0 atmosphere assumption must be accompanied by 0 gravity -- and the whole thought exercise becomes tautological, as the bullet would never fall.

Just for fun and games, though, let's say that the slight moon atmosphere has near zero effect, and that there is enough earth oxygen stored to light the powder in the shell. Fire the rifle and measure its speed as it leaves the muzzle versus its speed when it returns to the moon's surface. Use a fudge factor of about .2 to account for the difference between Earth and Moon gravity. Run the numbers and I think you'll find the muzzle speed is about 10 times greater than its speed when it hits the moon -- proving the original statement wrong -- the force of gunpowder is greater over the same time and space than the force of earth or moon gravity. So rockets do fly, and you can get to the moon.

Now leave the moon, and go to Jupiter. Do the same experiment with the same rifle, knowing that Jupiter has over 300 times the gravity of earth. The round barely leaves the tube and the science teacher is happy to have found a place where gravity is stronger than earthbound sized gunpowder rounds.

I think on the asteroid, the bullet never returns, because escape v = sqrt(2GM/R). For the largest asteroid I can find, that means <1000 mph velocity. A decent rifle round will leave the tube traveling at 1500 to 2500 mph with earth gravity. So, bye bye, it's gone. The moon's escape velocity is ~ 5000 mph.

When it comes to black holes, I give up. Far more theory than fact is known about them.

BUT

I did think about the problem a lot more, and just to make you happy; posted a solution above under the name: IT CAN BE DONE. Hope you find my solution a bit intersting and amusing.

Steve

One way to try it, not recomended though, is to fire your gun streight up into the air next to a shead with a tin roof. You know what would happen if you fired the gun streight up under the building. See if the falling bullet has the same affect.

I have done this with a compound bow, the arrow falling back to ground will not go punch a hole in the tin roof.

Here's another scientific curiosity - if you fired a projectile straight upward from a MOVING vehicle, and the vehicle continued to travel at the same velocity and direction, would the falling projectile hit the vehicle? Theoretically, the answer is YES. I'm a science teacher too, and my students and I launched hobby rockets off the roof of a moving car. Came awfully close to getting hit several times. Had there not been a slight breeze, I'm sure it would have.