Physics question

There is a (magic) B-17 flying along at 560 mph. The tail gunner is out of
..50 caliber ammo. He sees a Messerschmitt ME-109 crossing behind the B-17,
50 yards away.

He pulls out his trusty .45 Colt auto (muzzle velocity 820 fps) and fires at
the Hun when the ME-109 is directly behind the B-17. He leads the
Messerschmitt by exactly enough to hit the pilot (if he were firing from a
fixed position).

Does the bullet exit the muzzle and fall directly to earth?

Rich "Scratching my head" S.

In article ,
"Rich S." wrote:

There is a (magic) B-17 flying along at 560 mph. The tail gunner is out of
.50 caliber ammo. He sees a Messerschmitt ME-109 crossing behind the B-17,
50 yards away.

He pulls out his trusty .45 Colt auto (muzzle velocity 820 fps) and fires at
the Hun when the ME-109 is directly behind the B-17. He leads the
Messerschmitt by exactly enough to hit the pilot (if he were firing from a
fixed position).

Does the bullet exit the muzzle and fall directly to earth?

Rich "Scratching my head" S.


Yes, but the bullet is traveling at 820 ft/s relative to the B-17. The
bullet will drop straight down, but can still hit the ME, which runs int
the bullet.

Here's a wacky scenario... why can you fire a gun on the equator
in the direction of the setting sun? I mean, the Earth spins at
the equator at around 1,000 miles per hour (24,000 mile circum-
ference divided by 24 hr rotation), so why does the bullet exit
the barrel at the same velocity no matter what direction you
point it in? Hmmm. :-)

I think it's because the atmosphere is rotating at the same speed,
thus no friction to slow it down or keep it inside the barrel.

Yes? No? How does this differ from the first scenario?







Dean A. Scott, mfa
---------------------------------------
School of Visual Art and Design
southern adventist university
---------------------------------------
http://www.southern.edu/~dascott

("Dean A. Scott" wrote)
Here's a wacky scenario... why can you fire a gun on the equator
in the direction of the setting sun? I mean, the Earth spins at
the equator at around 1,000 miles per hour (24,000 mile circum-
ference divided by 24 hr rotation), so why does the bullet exit
the barrel at the same velocity no matter what direction you
point it in? Hmmm. :-)


Don't have an answer ...but pointy bullet shaped things + the equator = this
link.

http://www.qrg.northwestern.edu/projects/vss/docs/Navigation/2-why-launch-from-equator.html
"Why is it better to launch a spaceship from near the equator?"


Montblack

"Dean A. Scott" wrote in message
news:1126146846.d1f75da4b1eff1487f40a17ade08c409@t eranews...
Here's a wacky scenario... why can you fire a gun on the equator
in the direction of the setting sun? I mean, the Earth spins at
the equator at around 1,000 miles per hour (24,000 mile circum-
ference divided by 24 hr rotation), so why does the bullet exit
the barrel at the same velocity no matter what direction you
point it in? Hmmm. :-)

Imagine that the target is going away from you at the same speed that the
bullet is traveling. It would hit the ground before it reaches the target.
(Actually, it would never catch the target.

Now, turn that around. Imagine the target is standing still and you are
going away from it at bullet speed. Same ting happens, mon. De bullet hits
de ground.

Like incest, it's all relative.

Rich S.

With bullet/plane(s) relative horizontal speed of 820ft/s, the other
plane reaches the bullet position in (50x3)/820 = 0.183 sec (pretty
slow bullet). In that time the bullet falls a vertical distance of 0.5
x 32 x 0.183 x 0.183 ft = 0.536 ft. If the messer plane bottom was at
least 0.537 ft (about 7 inches) below bullet firing vertical position
its gona hit the other plane.

Ignoring air friction, whether the planes are moving or parked on the
ground with same separation it does not matter. It is only the relative
velocity of the bullet to the planes that counts. But with backward
airstream and downward friction the bullet will fall slower down than
in vacuum - so better chance of hitting the plane behind.

Is this your night school physics home assignment and you are cheating
here?

"abripl" wrote in message oups.com...
With bullet/plane(s) relative horizontal speed of 820ft/s, the other
plane reaches the bullet position in (50x3)/820 = 0.183 sec (pretty
slow bullet). In that time the bullet falls a vertical distance of 0.5
x 32 x 0.183 x 0.183 ft = 0.536 ft. If the messer plane bottom was at
least 0.537 ft (about 7 inches) below bullet firing vertical position
its gona hit the other plane.

Ignoring air friction, whether the planes are moving or parked on the
ground with same separation it does not matter. It is only the relative
velocity of the bullet to the planes that counts. But with backward
airstream and downward friction the bullet will fall slower down than
in vacuum - so better chance of hitting the plane behind.

Is this your night school physics home assignment and you are cheating
here?

"abripl" wrote in message oups.com...
With bullet/plane(s) relative horizontal speed of 820ft/s, the other
plane reaches the bullet position in (50x3)/820 = 0.183 sec (pretty
slow bullet). In that time the bullet falls a vertical distance of 0.5
x 32 x 0.183 x 0.183 ft = 0.536 ft. If the messer plane bottom was at
least 0.537 ft (about 7 inches) below bullet firing vertical position
its gona hit the other plane.

Ignoring air friction, whether the planes are moving or parked on the
ground with same separation it does not matter. It is only the relative
velocity of the bullet to the planes that counts. But with backward
airstream and downward friction the bullet will fall slower down than
in vacuum - so better chance of hitting the plane behind.

Is this your night school physics home assignment and you are cheating
here?


This would only work if the 109 was ahead of the 17 when the shot was fired.

This would only work if the 109 was ahead of the 17 when the shot was fired.

It will work fine as long as the two maintain the relative 50 yards
distance between them. - one following the other. Or is Rich S.
description of the motion muddled? I took "crossing behind the B-17" as
simply crossing the line of sight slightly and not a perpendicular
ground path. Normally a 109 would follow a B-17 to attack.

"abripl" wrote in message
oups.com...
With bullet/plane(s) relative horizontal speed of 820ft/s, the other
plane reaches the bullet position in (50x3)/820 = 0.183 sec (pretty
slow bullet). In that time the bullet falls a vertical distance of 0.5
x 32 x 0.183 x 0.183 ft = 0.536 ft. If the messer plane bottom was at
least 0.537 ft (about 7 inches) below bullet firing vertical position
its gona hit the other plane.

Nope. You are assuming "the other plane reaches the bullet position . . .".
It never reaches the bullet's position because it is traveling at 90° to the
flight path of the B-17. If it was following the B-17, it could possibly run
into the bullet, but only at its foward velocity. The bullet has only a
downward component relative to the Earth. (Ignoring minor variations, i. e.
coriolis force & wind velocity.)

Ignoring air friction, whether the planes are moving or parked on the
ground with same separation it does not matter. It is only the relative
velocity of the bullet to the planes that counts. But with backward
airstream and downward friction the bullet will fall slower down than
in vacuum - so better chance of hitting the plane behind.

Is this your night school physics home assignment and you are cheating
here?

Nope. Last physics course I took was at the U of Wash., 47 years ago. I
brought this subject up because I was reading an article in the May 1942
issue of "Flying and Popular Aviation". It was titled "Speedy" and tells the
story of a quiet young fellow named Andy McDonough who dove a new Army
fighter to 620 mph a "few weeks ago". He'd like to try for 700.

The airplane was a new P-39 Airacobra. "After his test, McDonough said he
thought of that now-famous problem: 'I wondered what would have happened if
I could have fired a pistol back over the tail. At that speed would the
bullet have rolled out of the barrel and then fallen back?'".

Well, perhaps that was a famous problem in the spring of 1942. I don't know,
having entered this vale of tears late in 1941. But I thought it would be
fun to toss it up here among all these reasonable, logical, polite folks.

Rich S.