Bullets falling back to earth

Space shuttle is the best example of that. And it isn't going anywhere near straight down.

Dave

The space shuttle in LEO is over 17,000 MPH; it has to slow down A LOT to just be going supersonic.

Best regards, Spehro Pefhany

On an airless planet but not on Earth. Think Areodynamic drag.

Ted

I think on earth too. The downward component of the areodynamic (sic) drag will be the same in both cases.

Now if you got some spin on the fired cannon ball, things might be different.

I believe it to be so on earth, aerodynamic drag will act upon the bullet's horizontal motion, gravity will act upon it's vertical drop. think about it a little more and you might agree.

JTMcC.

I'm aware of terminal velocity, and have reached it a time or two. I can reach it while falling from a height, regardless of my velocity in reaching that height, therefor my difference of opinion with the post about the bullet dropping at the same speed it initially rose. I can jump (fall, be pushed out of) an airplane at a height of 1000 ft and I will achieve a certain speed before wind resistance prevents any further increase. I can also be shot from a cannon straight into the air, or simply step off a platform at 1000 feet and still, my velocity toward the earth is limited by drag. If I spend 7 hours climbing to the 1000 foot mark, or ascend in a matter of seconds via F-16, my upward velocity matters not to the downward velocity I attain. That is my take, but then I wasn't even paying attention in H.S. physics.

JTMcC.

Even on earth.

Basic physics has us break things up into components. A cannon ball fired exactly horizontal will have tremendous velocity horizontally, and none vertically. While the horizontal velocity will be decreasing due to friction with the air, the vertical velocity will be increasing due to gravity. This increase works just the same as if you dropped the bowling ball. So a bowling ball dropped from the same height as the muzzle of the cannon will reach the ground in the exact same time as the cannon ball that was fired from the cannon (neglecting curvature of the earth and other such factors such as spin on the ball producing lift, etc.). Since both cannon balls are the same size and mass and have the same initial conditions in the vertical direction, they are for all intents and purposes identical in behavior on the vertical axis. Horizontal is obviously a different ball of wax.

-- Joe

-- Joseph M. Krzeszewski Mechanical Engineering and stuff snipped-for-privacy@wpi.edu Jack of All Trades, Master of None... Yet

Wouldnt the Shuttle have started out way up up beyond Mach 50, and slows down as it enters atmosphere, ultimately falling below supersonic as it finds its terminal velocity? Its actually slowing, rather than speeding up as it falls.

The Mach 50 figure being sheer hyperbole as there is no speed of sound in orbit.

Gunner

" ..The world has gone crazy. Guess I'm showing my age... I think it dates from when we started looking at virtues as funny. It's embarrassing to speak of honor, integrity, bravery, patriotism, 'doing the right thing', charity, fairness. You have Seinfeld making cowardice an acceptable choice; our politicians changing positions of honor with every poll; we laugh at servicemen and patriotic fervor; we accept corruption in our police and bias in our judges; we kill our children, and wonder why they have no respect for Life. We deny children their childhood and innocence- and then we denigrate being a Man, as opposed to a 'person'. We *assume* that anyone with a weapon will use it against his fellowman- if only he has the chance. Nah; in our agitation to keep the State out of the church business, we've destroyed our value system and replaced it with *nothing*. Turns my stomach- " Chas , rec.knives

Seems they have an edge over East L.A.

Gunner

" ..The world has gone crazy. Guess I'm showing my age... I think it dates from when we started looking at virtues as funny. It's embarrassing to speak of honor, integrity, bravery, patriotism, 'doing the right thing', charity, fairness. You have Seinfeld making cowardice an acceptable choice; our politicians changing positions of honor with every poll; we laugh at servicemen and patriotic fervor; we accept corruption in our police and bias in our judges; we kill our children, and wonder why they have no respect for Life. We deny children their childhood and innocence- and then we denigrate being a Man, as opposed to a 'person'. We *assume* that anyone with a weapon will use it against his fellowman- if only he has the chance. Nah; in our agitation to keep the State out of the church business, we've destroyed our value system and replaced it with *nothing*. Turns my stomach- " Chas , rec.knives

A 30.06 rifle bullet has a muzzle velocity almost 3000 ft. per second. This equates to approx.2045.5 mph. a bullet falling straight back to earth has the law of gravity pulling it and with wind resistance will attain a velocity of approx. 150 mph. which equates to about 102 ft per second. about the weakest firearm cartridge there is a .25 cal and it's muzzle velocity is over 500 ft. per second which is five times the speed of a falling bullet and a .25 cal. is so weak that very often when someone is shot with one all it does is get them mad where as they take the gun away and wip your ass.

Sorry, it's a very poor example - nearly as poor as my wording in the previous comment.

I should have said "reached terminal velocity in free fall", with the emphasis on "reaching". The shuttle is fast when it arrives, and getting slower all the way down. If you dropped a stationary shuttle from altitude, it certainly wouldn't _go_ supersonic.

According to a book entitled "Hatcher's Notebook", the US Army performed tests in Florida swamps in the first half of the 20th century by firing a 30 cal. machine gun straight up into the air and carefully evaluating the returning bullets. They determined that the returning 30 cal. 150 grain bullet would reach a maximum terminal velocity less than that required to penetrate the skull of an adult male, or reliably cause a disabling wound. The terminal velocity was limited by the air resistance acting on the bullet as it fell, thus limiting its impact energy. However a falling 50 cal bullet, due to its greater mass, was considered a lethal threat. Don't try this at home! If you want more details, the book is interesting reading. JM

Well there has to be. How else could stuff go "boom" in space, in all those movies?

LOL

Jim

================================================== please reply to: JRR(zero) at yktvmv (dot) vnet (dot) ibm (dot) com ==================================================

Notwithstanding Gunners report i would suggest that a bullet falling vertically is more likely to cause a head injury than one moving with a lower trajectory. The Army estimates for energy required to inflict a mortal wound were probably not specific to head wounds. If the bullet has enough energy to penetrate the skull, then it probably has enough energy to cause a fatal wound.

Mark Rand RTFM

If the .25 cal goes 500 ft/s, thats around 341 mph... have you ever been close to something going that fast? I have... and I'm sure wouldn't want to be hit by anything going that fast.

Back in the old skydiving days, a guy still in freefall grazed the skirt of an open canopy with his hand & lower arm. He probably had a closing speed of about 110 mph (only a measly 161.3 ft/s). Thats 120 mph terminal freefall speed minus the roughly 10 mph decent speed of the open round canopy.

Neither he, or the other two witnesses thought any part of the canopy or lines had wrapped around him in any way... but wow, what mess it made of him... multiple compound fractures, and all the fun associated stuff that goes with them.

I think if I were shot with a .25, and ended up only being mad, I'd be VERY lucky.

Erik

Actually, there was a man that went supersonic in free fall! IIRC, it was post W.W.II and the Air Force sent an officer up in a balloon. _Really_ up, like altitude record high. He jumped out and did free fall for a _long_ time. Since he was so high, the speed of sound was considerably less than at sea level (air density thing) and he actually exceeded it.

Or so I heard on the Discovery channel, or TLC - one of them.

Bob

I would think a round lead ball would be the most dangerous. No tumbling to cut down on drag and quick terminal velocity. An ounce lead ball shot skyward with a good sling shot might reach terminal velocity on the way down and I sure wouldn't won't to be on the receiving end of it.

In World War I the French used "flechettes" against the troops in the trenches. These were machined steel darts a few inches long, with flutes cut into the aft end to stabilize and rotate them. They were dropped from airplanes at a considerable height, hundreds at a go, and would reach transsonic speeds (one source claimed supersonic speeds, but I think the drag would preclude that)before they hit the ground or some unfortunate soldier. Helmets weren't much protection; they were sharp. The density of air at 18,000 feet is half of that at sea level. Anything dropped from this altitude is going to accelerate much more quickly, as drag is a function of the square of any increase in speed. Half of the density should, I figure, cut the drag to a quarter. Increasing drag at lower altitudes would slow the acceleration, but a much higher final velocity should be possible for a dart.

Dan

Mark sez: "Notwithstanding Gunners report i would suggest that a bullet falling vertically is more likely to cause a head injury than one moving with a lower trajectory. The Army estimates for energy required to inflict a mortal wound were probably not specific to head wounds. If the bullet has enough energy to penetrate the skull, then it probably has enough energy to cause a fatal wound."

Hmmnnnn? I wonder about that. Without doing the ballistic research thing, it would seem that a bullet moving with any trajectory at all would still have a remaining horizontal component of velocity. Thus, I believe the lower trajectory bullet, i.e., stray bullet, would be the more dangerous.

Bob Swinney