Physics question

Rich S. wrote:
"T o d d P a t t i s t" wrote in message
...
"RST Engineering" wrote:

No, the ME-109 has zero relative velocity in the B-17s flight path...he
said
CROSSING 50 yards behind the aircraft.

True, he said "crossing," but he also said he's leading the
ME-109, and I specified that he fires straight back, i.e.,
he leads the ME-109 so that he's aiming at the point where
the ME-109 crosses the B-17s flight path.

The bullet drops straight down (relative to the ground).
The ME-109 flies into it before it drops significantly.

Perhaps I wasn't clear. Maybe I can diagram it.

Aiming
point
. ----- ME-109

B-17
|
V


In your text you said the gunner fies when the ME 109
is directly behind the B17. For orthogonal ground
tracks, he cannot hit the ME 109 if it is *anywhere* behind
the B17 no matter where he aims because the flight
paths of the ME 109 cannot intersect the path
the bullet takes to the ground.


In your illustration, the gunner fires straight back
before the Me-109 is directly behind the B17. He can hit
if he fires at precisely the moment his gun crosses the
flight path of the Me-109.

--

FF

wrote in message
oups.com...

In your text you said the gunner fies when the ME 109
is directly behind the B17. For orthogonal ground
tracks, he cannot hit the ME 109 if it is *anywhere* behind
the B17 no matter where he aims because the flight
paths of the ME 109 cannot intersect the path
the bullet takes to the ground.

That's why, in the text, I also added that he "led" the ME-109 exactly
enough. Did you read the entire sentence? As I said, perhaps I wasn't clear.
He fires directly behind the B-17. The ME-109 is on its way to cross the
flightpath of the B-17.

In your illustration, the gunner fires straight back
before the Me-109 is directly behind the B17. He can hit
if he fires at precisely the moment his gun crosses the
flight path of the Me-109.

Not so. The bullet simply falls to Earth and the ME-109 passes safely 50
yards (or so) behind the B-17.

Rich "Don't use them 3-silable words like 'orthogonal'" S.

He misses the ME-109 because the recoil of firing the bullet
accelerates the B-17 just a bit, so that the bullet, travelling at a
little less than the bomber's speed actually briefly follows the bomber
as it falls.

A related question: Haven't there been cases of supersonic
fighters shooting themselves down when they caught up to the shells
they'd fired forward?

Dan

(Dan_Thomas_nospam wrote)
He misses the ME-109 because the recoil of firing the bullet
accelerates the B-17 just a bit, so that the bullet, travelling at a
little less than the bomber's speed actually briefly follows the bomber
as it falls.

Plus there is a constant speed with the B-17. The bullet needs to accelerate
to reach that same speed. g


A related question: Haven't there been cases of supersonic
fighters shooting themselves down when they caught up to the shells
they'd fired forward?

'If I drive the speed of light, and turn on the headlights - would anything
happen?' Steven Wright ...and maybe also "The Lazlo Letters" (1977) by Don
Novello.


Montblack

wrote:
He misses the ME-109 because the recoil of firing the bullet
accelerates the B-17 just a bit, so that the bullet, travelling at a
little less than the bomber's speed actually briefly follows the bomber
as it falls.

A related question: Haven't there been cases of supersonic
fighters shooting themselves down when they caught up to the shells
they'd fired forward?

Dan

I was hoping someone would answer that. I recall seeing/hearing/reading
somewhat the same thing back when. Best I can recall it involved an
F-86 or equivalent (not supersonic) and happened by firing and then
going into a dive thus flying into the bullet stream. Are 50 cal
bullets supersonic?
If so, the plane would also have to be.

Harry K

In article .com,
"Harry K" wrote:

wrote:
He misses the ME-109 because the recoil of firing the bullet
accelerates the B-17 just a bit, so that the bullet, travelling at a
little less than the bomber's speed actually briefly follows the bomber
as it falls.

A related question: Haven't there been cases of supersonic
fighters shooting themselves down when they caught up to the shells
they'd fired forward?

Dan

I was hoping someone would answer that. I recall seeing/hearing/reading
somewhat the same thing back when. Best I can recall it involved an
F-86 or equivalent (not supersonic) and happened by firing and then
going into a dive thus flying into the bullet stream. Are 50 cal
bullets supersonic?
If so, the plane would also have to be.

Harry K

No it wouldn't.

Quick question: what does a plane have that a bullet lacks?

Answer: an engine to maintain its speed.

Bullets start slowing down the moment they leave the muzzle (alright,
just slightly *after* they leave the muzzle), while the aircraft that
fired them can maintain its speed.

--
Alan Baker
Vancouver, British Columbia
"If you raise the ceiling 4 feet, move the fireplace from that wall
to that wall, you'll still only get the full stereophonic effect
if you sit in the bottom of that cupboard."

Quick question: what does a plane have that a bullet lacks?


Answer: an engine to maintain its speed.


Bullets start slowing down the moment they leave the muzzle (alright,
just slightly *after* they leave the muzzle), while the aircraft that
fired them can maintain its speed.

But in this case there is no air friction to "slow" the bullet.
It leaves the gun into still air, and so if the bomber is accelerated a
bit by the gun's recoil, its muzzle velocity is a bit less than the
airplane's velocity and so will move "forward" a little as it falls.


Dan

In article .com,
wrote:

Quick question: what does a plane have that a bullet lacks?


Answer: an engine to maintain its speed.


Bullets start slowing down the moment they leave the muzzle (alright,
just slightly *after* they leave the muzzle), while the aircraft that
fired them can maintain its speed.

But in this case there is no air friction to "slow" the bullet.
It leaves the gun into still air, and so if the bomber is accelerated a
bit by the gun's recoil, its muzzle velocity is a bit less than the
airplane's velocity and so will move "forward" a little as it falls.


Dan

Read the question I answered...

A related question: Haven't there been cases of supersonic
fighters shooting themselves down when they caught up to the shells
they'd fired forward?

Dan

I was hoping someone would answer that. I recall seeing/hearing/reading
somewhat the same thing back when. Best I can recall it involved an
F-86 or equivalent (not supersonic) and happened by firing and then
going into a dive thus flying into the bullet stream. Are 50 cal
bullets supersonic?
If so, the plane would also have to be.


--
Alan Baker
Vancouver, British Columbia
"If you raise the ceiling 4 feet, move the fireplace from that wall
to that wall, you'll still only get the full stereophonic effect
if you sit in the bottom of that cupboard."

Harry K wrote:
wrote:
He misses the ME-109 because the recoil of firing the bullet
accelerates the B-17 just a bit, so that the bullet, travelling at a
little less than the bomber's speed actually briefly follows the bomber
as it falls.

A related question: Haven't there been cases of supersonic
fighters shooting themselves down when they caught up to the shells
they'd fired forward?

Dan

I was hoping someone would answer that. I recall seeing/hearing/reading
somewhat the same thing back when. Best I can recall it involved an
F-86 or equivalent (not supersonic) and happened by firing and then
going into a dive thus flying into the bullet stream. Are 50 cal
bullets supersonic?
If so, the plane would also have to be.

I don't know the muzzle velocity of 50 caliber ammo but even it
is supersonic, it is balistic whereas the plane is powered so
it could (maybe) dive and catch the bullets as they slowed.

--

FF

Rich S. wrote:
wrote in message
oups.com...

In your text you said the gunner fies when the ME 109
is directly behind the B17. For orthogonal ground
tracks, he cannot hit the ME 109 if it is *anywhere* behind
the B17 no matter where he aims because the flight
paths of the ME 109 cannot intersect the path
the bullet takes to the ground.

That's why, in the text, I also added that he "led" the ME-109 exactly
enough. Did you read the entire sentence?

Yes, you added the condition that he leads by exactly the same
amount he would from a fixed condition to the statement that
he fires when the ME-109 is directly behind the B17.
If he waits to fire until after the B17 has crossed the
flight path of the ME 109 he cannot hit no matter how
he aims. It matters not how he leads.


As I said, perhaps I wasn't clear.
He fires directly behind the B-17. The ME-109 is on its way to cross the
flightpath of the B-17.

This you added in a later post. If, while firing straight back
he still leads as if he were firing from a fixed position he
will miss again because the B17 has already crossed the flight
path of the ME-109 by the time he fires.

No matter the direction, if he fires after the B17 has
crossed the flightt path of the ME-109 he misses.



In your illustration, the gunner fires straight back
before the Me-109 is directly behind the B17. He can hit
if he fires at precisely the moment his gun crosses the
flight path of the Me-109.

Not so. The bullet simply falls to Earth and the ME-109 passes safely 50
yards (or so) behind the B-17.

That is true if he leads the ME109 as he would from a fixed
position, or any way other than the *right* way. But there
is a right way. I *changed* the scenario when I said he
fires at precisely the moment his gun crosses the flight
path of the ME-109.

If he fires stright back at that moment,
and the ME 109 is flying at the same airspeed as
the B-17 then the bullet is *also* 50 yards behind the
B17, when the ME-109 crosses. It will be a half inch or
so lower than the altitude at which it exited the muzzle
if it was fired exactly level.

Firing straight back at the moment the B17 crosses the
flight path of the ME-109 essentially drops the bullet
through the flight path of the ME-109. IF the bullet is
still there when the ME-109 arrives, which it will be
for a range of speeds close the speed of the B17,
the gunner hits.

An the gunner can compensate for the ME-109 flying
at a different speed and altitude by firing up or
down a little, again for some range of speeds and
altitudes.

--

FF