Silly ballistic questions + a cool game...

[possenti]

I never gave it much thought, but to get the maximum distance from a fired projectile, is the optimum angle for the weapon 45 degrees? I began wondering when I was playing this online Flash game:

http://sapporo.cool.ne.jp/f1ash/flash/bowman.swf

Considering all shots are fired with the same force, and using the same projectile weight, it makes sense.

Silly question #2:

Unlike an arrow, which has tail fins to provide wind resistance - it's been said that a bullet fired straight up into the air (90 degrees) will go up and come straight down, landing on its base, because the forward inertia runs out before the stabilizing spin. Makes sense to me...

At what angle does the bullet "turn" in flight so the point impacts the ground first? Below 45 degrees?

Also - under 45 degrees, does the bullet "pitch" to match the arc of flight, or does it stay at the same angle that it left the barrel, due to the stabilizing spin? I suspect it follows the arc, since they don't leave "keyholes" in paper targets. But following the "90 degree rule", it should stay at the same angle, shoudn't it?

I'm not a physics expert, and I apologize for using layman's (or incorrect) terms. However, if anyone can figure out what the hell I'm asking, I'll do my best to understand a technical explanation.

 

[Zak Smith]

The optimium angle is less than 45 degrees because of wind resistance. In a vacuum, a sphere would go the furthest if you fired it at a 45 degree angle - simple physics tells you that. With atmosphere, the "closer" you are to no air (ie, the higher BC, or the lower the MV) the closer to 45 degrees the max will be.

For example, there isn't much loss due to air resistance if you throw a baseball at 5fps. On the other hand, if you launch a low-BC bullet at 4000fps, wind resistance effects will be large.

For your second question, it will depend on the rotational inertia of the bullet relative to the transverse torque applied by the center of drag being offset from the bullet's direction vector. If the bullet is spinning faster (ie, massively over-stabilized) it will be able to "resist" rotating longer.

-z

 

[Kevlarman]

Haha, this is a fun game!

 

[Billll]

I found a neat article once on the physics of bullets that described the path of a rifle bullet (long and narrow) over an arc as having the nose trail the actual angle of flight by a small amount, about 2-5 deg. Also the nose will be tilted slightly to the right or left, due to the interaction of the spin of the bullet with the air.
Pistol bullets, (short and fat) tend to be "over stabilized" when spun at the same twist rates as rifle bullets. Thus, a (.45 for example) pistol bullet fired upwards at 45 deg, will be tipped up at 45 deg when it hits the ground.
I'll see if I can find the article.
Best range angle depends on the ballistic coefficient of the projectile. For pumpkins, for example, it's about 40 deg.

 

[DonNikmare]

Fun game! Lost once but got the puter with two head shots/arrows the second time

Nik

 

[entropy]

A friend and I used to do that, play 'chicken' with arrows. We also stood about 200 yds. away from each other and shoot to see who got closest without hitting the other .(Well, at least that's what he told me )
It's a wonder I ever reached adulthood.

 

[P95Carry]

It's a wonder I ever reached adulthood.

Often think that entropy but in my case ... I'd also say - I haven't reached adulthood yet! Still 16 goin on 59.!!

When I decide I have grown up then, well ... probably time to bury me for being not just an ol' phart but ..... a BORING ol' phart!!

If you're still able to have fun ... you're doin OK!

 

[entropy]

Well, yeah, I hear ya! I meant physical adulthood. I probably will never get to emotional or psychological adulthood!

 

[Red_SC]

As already mentioned, the optimum angle to get farthest bullet flight is a little less than 45 degrees because of wind resistance. Also, a bullet doesn't stay pointed at the same angle during flight. The bullet shape makes it stay pointing close to the direction of travel. I did read some interesting things about this once. Somebody was shooting some VLD rifle bullets (long, pointy bullets designed for very low drag) and overstabalized them. At longer ranges, the velocity was suddenly dropping very rapidly, and the trajectory would drop. They eventually figured out that the bullet was so stabalized that it was staying pointed at the same angle through the whole flight. When it reached the highest point in its trajectory and started falling, it was basically flying sideways, and the drag would slow it down quickly.

This was with rifle bullets, though. I'm sure pistol bullets behave differently.

 

[Indy7373]

This game is quite addicting.

 

[Reno]

I can't say what the angle is for the extreme high speeds of a bullet, but at 50m/s, the optimum angle is ~38 degrees.

 

[Red_SC]

Actually, Reno, the number I had in my head was 39 degrees. I didn't mention it because I can't remember where I got it, so I'm not sure it's right.

 

[Reno]

It's something along those lines. I had to figure it out for a can launching project this past semester, built a triple leaf spring crossbow. We just used a computer simulation though, and could only adjust to single degrees. Didn't really care to find an analytical solution.