If a bullet falls . . .

From Straight Dope Classics

Regarding the column about a fired bullet versus a dropped bullet (which hits the ground first), wouldn’t there be some sort of “float” or wing effect; would Bernoulli’s Principle have an effect on the fired bullet?

Not if the bullet has an identical angle of attack on the top and bottom. For Bernoulli’s force to create lift, the air traveling across the top has to be slower than the air on the bottom. The faster moving air exerts less pressure. More pressure on the bottom than on the top creates your lift.

I see what you mean, Thor. I guess, then what I am asking is, is there a glide element to a bullet’s flight, like a paper airplane, or for that matter, a piece of paper?

Dont think the glide argument will work, but how about the curvature of the earth. Since it is traveling horizontally it is in a very very short orbit and when it falls back to earth the earth is just a little further away

the question din’t say anything about the angle relative to earth. if the gun were absolutely level (tangent) and you encountered no updraft and the landing points had the same altitude, then they would land at the same time. If it were slightly up, the bullet would have to rise before it falls. pointed down, it would hit sooner.
also, doesn’t the bournelli effect state that fast-moving air creates a partial vacuum. the top of the bullet would have a greater curve than the bottom for the thing to glide. any rifled firearm would make the bullet spin, so no top or bottom. I don’t know how a smooth-bore weapon would act.
Not enough information to do anything.

Can a gun fire a bullet far enough for the curviture to make a measurable difference?

Assuming that altitude means “height above sea level”, then the fact that the landing points have the same altitude has no impact on the question at hand. A point that is 100 yards away, but at the same altitude as you, is below the tangent from where you stand. More on this below.

Based off what? I think that you are mixing up your pronouns here; does the last it (“it would hit sooner”) refer to the dropped bullet? It seems to refer to the bullet fired up.

I believe so. The Sharps-50 buffalo gun can fire in excess of one mile; I don’t have the math, but I’m pretty certain that a mile circumference will result in a measurable amount of curve (granted, not large, but measurable). A bullet fired on the tangent will have to drop further than one that doesn’t move horizontally, so if all other factors remain the same, the fired bullet would take longer to drop.

I thought Cecil covered all this though; including the observation that if the bullet was fired fast enough it would enter orbit and never hit the ground :slight_smile:

Come on guys–remember high school physics and the falling monkey trick? The idea is that you assume the conditions for the bullet falling are perfect. Because of imperfections in the spherical shape of the earth, the trick cannot really work. But on a theoretical perfectly flat plain, with a gun perfectly level, no wind resistance or Bernoulli effects to contend with, the bullet leaving the barrel of the gun and the bullet falling will hit the ground at exactly the same time.
Any physics teacher worth his salt will have a little spring loaded apparatus that launches a ball horizontally and drops one at the same time. Go your local high school and ask for a demo.

Aren’t we all forgetting the fact that the downward force of gravity plays no role UNTIL the projectile leaves the end of the gun barrel? Assuming one bullet is dropped and the other fired at the same time (and nothing more than is stated in the original question), the dropped bullet hits the ground first for no other reason than the fact that it has a head start, albeit a tiny one, on the gun bullet.


jhigham, you are correct. I stated my point poorly. I was trying to point out that as the fired bullet travels, the direction of gravity changes also. If you aim the barrel perfectly paralell to an earth tangent, with the exit point directly above the tangent point, then at the moment the bullet leaves the barrel, its initial vertical velocity is zero. The fired bullet only has initial horizontal velocity. At that same moment gravity starts to affect it. It will accellerate towards the center of the earth at 9.8m/s^2 regardless of how far it travels around the face of the earth. . . if no wind gusts or mountains get in the way.
However this point is now moot. I forgot about the head start.

Personally i’m a fan of the chaos theory. I think there are too many eliments to consider here. Yes, in a perfect vacum with a great distance, blah blah blah … they would probably hit the ground at the same time. However EXACTLY is too strong of a word for me. With the amount of variables to consider in the real world i doubt anyone could create an environment to test this theory in. lol … so there. :slight_smile:

verdict: ANSWER DOES NOT MATTER.