Physics question

Rich S. wrote:
"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 =3D 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 =3D 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.

Half a foot at 50 yards? I misrememeberd that a 45 drops half an
inch at 50 yards. How embarassing.


Nope. You are assuming "the other plane reaches the bullet position . . .=
"=2E
It never reaches the bullet's position because it is traveling at 90=B0 t=
o 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=2E
coriolis force & wind velocity.)


You're still assuming he's leading the ME-109 as if the gunner
were in a fixed location. He's assuming the gunner is actually
trying to hit the plane, and smart enough to figure out how
so that he times his shot *correctly*. You're both assuming
he fires straight back. He can hit the Me-109 by firing straight
back, but ONLY if he fires exactly as B-17 crosses the flight
path of the Me-109, and only if the Me-109 is fast enough or
close enough to get there before the bullet drops out of the
flight path of the Me-109. If the Me-109 is at a range of 50
yards, and no slower than the bullet the bullet will be no
more than 7 inches lower than the muzzle of the gun and will
still hit the Me-109 assuming the two planes are at the same
altitude.

Here is an example:

Both planes are at the same altitude.
The gunner fires straight back and level when the B-17
crosses the flight path ahead of the ME-109. At that
moment, the Me-109 is at a range of 50 yards, e.g. it
is 50 yards directly to the right of the gunner and
flying from right to left, and also flying at 820 ft/s.
If you think that bullet misses, calculate by how much.
Now do that again, assuming the Me-109 is a bit faster,
say, 900 ft/s.

There is a range of realistic speeds and altitudes
for the Me 109 for which it will be hit, and a larger range
of speeds an altitudes for which it can be hit if the gunner
is allowed to aim up or down, larger still if he can aim from
left to right even though in all cases the ME-109 is flying
at 90 degrees to the flight path of the B-17.

--=20

FF

wrote in message
ups.com...

You're still assuming he's leading the ME-109 as if the gunner
were in a fixed location. He's assuming the gunner is actually
trying to hit the plane, and smart enough to figure out how
so that he times his shot *correctly*. You're both assuming
he fires straight back. He can hit the Me-109 by firing straight
back, but ONLY if he fires exactly as B-17 crosses the flight
path of the Me-109, and only if the Me-109 is fast enough or
close enough to get there before the bullet drops out of the
flight path of the Me-109. If the Me-109 is at a range of 50
yards, and no slower than the bullet the bullet will be no
more than 7 inches lower than the muzzle of the gun and will
still hit the Me-109 assuming the two planes are at the same
altitude.

Fred...............

I'll say it again - you misunderstand the question. I have stated it as
clearly as I am able and even drawn a diagram. I don't know how else to
explain it. I'm a pilot. I talk with my hands (hopefully without resorting
to certain gestures).

The B-17 is flying West. The ME-109 is flying South. They are both at the
same altitude. There is no wind. The ME-109 will cross the flight path of
the B-17 and the B-17 will, at that moment, be fifty yards from the ME-109.
The tail gunner fires his weapon straight behind the B-17.

There is no way that he can hit the ME-109, given the stated speed of the
B-17 and the muzzle velocity of the bullet.

The ME-109 will *always* be fifty yards or more away from the bullet.
Always.

Rich S.

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

You're still assuming he's leading the ME-109 as if the gunner
were in a fixed location. He's assuming the gunner is actually
trying to hit the plane, and smart enough to figure out how
so that he times his shot *correctly*. You're both assuming
he fires straight back. He can hit the Me-109 by firing straight
back, but ONLY if he fires exactly as B-17 crosses the flight
path of the Me-109, and only if the Me-109 is fast enough or
close enough to get there before the bullet drops out of the
flight path of the Me-109. If the Me-109 is at a range of 50
yards, and no slower than the bullet the bullet will be no
more than 7 inches lower than the muzzle of the gun and will
still hit the Me-109 assuming the two planes are at the same
altitude.

Fred...............

I'll say it again - you misunderstand the question. I have stated it as
clearly as I am able and even drawn a diagram. I don't know how else to
explain it. I'm a pilot. I talk with my hands (hopefully without resorting
to certain gestures).

The B-17 is flying West. The ME-109 is flying South. They are both at the
same altitude. There is no wind. The ME-109 will cross the flight path of
the B-17 and the B-17 will, at that moment, be fifty yards from the ME-109.
The tail gunner fires his weapon straight behind the B-17.

There is no way that he can hit the ME-109, given the stated speed of the
B-17 and the muzzle velocity of the bullet.

The ME-109 will *always* be fifty yards or more away from the bullet.
Always.

Rich S.

The way I see it, you are both in agreement. Fred says to hit the 109
he has to fire at the exact time the 17 croses the 109's path. That is
correct. In effect he says that to fire as per your example he can't
hit it.

Harry K

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

You're still assuming he's leading the ME-109 as if the gunner
were in a fixed location. He's assuming the gunner is actually
trying to hit the plane, and smart enough to figure out how
so that he times his shot *correctly*. You're both assuming
he fires straight back. He can hit the Me-109 by firing straight
back, but ONLY if he fires exactly as B-17 crosses the flight
path of the Me-109, and only if the Me-109 is fast enough or
close enough to get there before the bullet drops out of the
flight path of the Me-109. If the Me-109 is at a range of 50
yards, and no slower than the bullet the bullet will be no
more than 7 inches lower than the muzzle of the gun and will
still hit the Me-109 assuming the two planes are at the same
altitude.

Fred...............

I'll say it again - you misunderstand the question.

NO. I understood the question(s) and I answered them. The gunner
cannot hit the ME 109 by aiming and firing the ways you
described. There are an infinite number of ways the gunner
can aim and fire and miss, you picked some of them.

You also stated multiple versions with different
circumstances, not just different wording. It is not clear
that you realize that.

After answering YOUR questions, we then addressed the question
of how the gunner could hit the ME 109. That question was
NOT your question. That is a different question and I
don't see how I can make THAT any clearer to you.

No rule of nettiquette requires that we limit our discussion
to only the case you present. You are not the boss of us!
Courtesy requires that we make it clear when and how we
change the statement of the problem. We have made that
clear. You just don't realize that. We changed the
problem by relaxing the constraint on when the gunner
leaving him free to fire whenever he wants to.

Why? Because we're Americans goddamnit we want him
to score a hit. What are you, German?

clearly as I am able and even drawn a diagram. I don't know how else to
explain it. I'm a pilot. I talk with my hands (hopefully without resorting
to certain gestures).

The B-17 is flying West. The ME-109 is flying South. They are both at the
same altitude. There is no wind. The ME-109 will cross the flight path of
the B-17 and the B-17 will, at that moment, be fifty yards from the ME-109.
The tail gunner fires his weapon straight behind the B-17.

In *this* statement of the question, unlike
your first, you do not say WHEN he fires.
Since I WANT him to hit, I'll tell YOU
when he fires.

Got it!

He can hit the ME-109 by firing when the B17 crosses the flight
path of the ME-109. Then the Me-108 is due North of the gunner.
If he waits any longer, the Me-109 passes east of the bullet.
If he fires sooner, the Me-109 passes West of the bullet.

If he fires when the ME 109 is due North the Me-109 either
hits the bullet or passes over it depending on the range and
speed of the Me-109.

You specified that the Me-109 passes fifty yards behind
the B-17. A hit requires that the time
between firing and the time the ME-109 arrives behind the
B-17 is the time it takes the B-17 to travel 50 yards.
OP already calculated that, and also calculated that the
bullet drops 7 inches in that time. You did not
specify the speed of the ME-109 or the range when the
gunner fires, so we are free so vary those as needed.
there are several combinations of speed and range that
allow the ME-109 to be due North when he fires and
cross 50 yards behind. For instance, if the Me-109
is flying at the same speed as the B-17 and it crosses
50 yards behind it, then the Me-109 will also be 50 yards
when it is due North of the B-17 and the gunner can therefor
fire when the B17 is at a range of 50 yards and hit.
What a coincidence!

This time around I did not have to change the problem
because this time around you did not constrain the time
at which the gunner fires.



There is no way that he can hit the ME-109, given the stated speed of the
B-17 and the muzzle velocity of the bullet.

Wrong. The way is if he fires WHEN the B-17 crosses the flight path
of the Me-109. That drops a bullet in the flight path of the Me-109
and if the Me-109 is 50 yards due North when the gunner fires and
flying at 820 fps the Me-109 and the bullet are *both* 50 yards
behind the B-17 when the Me-109 crosses the flight path of the
B-17. The bullet has only dropped 7 inches, so it hits.


The ME-109 will *always* be fifty yards or more away from the bullet.
Always.


Not if the gunner fires when the B17 crosses the flight path of
the Me-109. That drops the bullet right in the flight path
of the Me-109 and the Me-109 closes on it as it drops.

Here is a hint. If you constrain all of the variables to specific
values the question is 'does', not 'can'. 'Can' implies at least
on variable is unconstrained as in your question above wherein
you left the time at shich the gunner fires free to vary.

--

FF

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.


Forgetting turbulence following the B-17 the bullet would still have
a muzzle velocity of 900 FPS, assuming a military load. 50 yards is 50
yards and the Me109 would still be hit assuming proper aim. Whether it
does much more than penetrate the canopy I don't know. Put the trailing
turbulence back into the scenario and all bets are off.

Dan, U.S. Air Force, retired

"Dan, U.S. Air Force, retired" wrote in message
news:cdOTe.9805$dm.6970@lakeread03...

Forgetting turbulence following the B-17 the bullet would still have a
muzzle velocity of 900 FPS, assuming a military load. 50 yards is 50 yards
and the Me109 would still be hit assuming proper aim. Whether it does much
more than penetrate the canopy I don't know. Put the trailing turbulence
back into the scenario and all bets are off.

Remember, the ME-109 is not following the B-17. It is crossing behind the
B-17 at 90° and is fifty yards behind the bomber at the moment their flight
paths cross. The bullet comes out of the muzzle with a velocity of 820 fps
relative to the pistol. The pistol however, is traveling 820 fps in the
opposite direction relative to the ME-109. Therefore the bullet has zero
velocity toward the ME-109 and drops straight down due to gravity.

Rich S.

You've made an irrelevant assumption here.


The answer is "It's all a matter of relativity"
With the correct lead, it does not matter what speed relative to the ground
the bullet is travelling, relative to the two aircraft is what is important.
remember the bullet is spinning so also maintains some gyroscopic stability.

All bullets fall to earth at 9.8 m/s^2 regardless of their path over the
surface of the earth.

With the correct lead the bullet and the ME-109 colide, at which point the
tragectory of the bullet is drasticaly altered such that it, and teh ME-109
all fall/fly to earth as one mass.

If the case is simplified such that the bullet is simply fired backwards but
at nothing, then it will accelarate to earth, only with a 0 lateral velocity
relative to the ground.


Rgds,

"Rich S." wrote in message
...
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.

Several people, most of whom have at least had physics, and at least one
with a degree in physics have stated that you are wrong and why. Suggest
you read the thread before you post.

Jim



"BRO" wrote in message
...




With the correct lead the bullet and the ME-109 colide, at which point the
tragectory of the bullet is drasticaly altered such that it, and teh
ME-109 all fall/fly to earth as one mass.

RST Engineering wrote:
Several people, most of whom have at least had physics, and at least one
with a degree in physics have stated that you are wrong and why. Suggest
you read the thread before you post.
...


"BRO" wrote in message
...




With the correct lead the bullet and the ME-109 colide, at which point the
tragectory of the bullet is drasticaly altered such that it, and teh
ME-109 all fall/fly to earth as one mass.


No. With the _correct_ lead he can hit.

The _correct_ lead is different from how he would lead if
he was firing from a fixed position.

The _correct_ lead is incompatible with firing when the ME-109 is
directly behind the B-17. He cannot correctly lead the Me-109
AND fire when the Me-109 is directly behind the B-17. But he
CAN correctly lead AND fire straight back.

In fact, he correct lead if the ME is at a range of 50 yards,
when the B17 crosses the flight path of the ME-109,
is to fire straight back. Then he will hit when the Me-109
is fifty yards behind the B-17.

The problem is not with what he said, but with what he did
not say. He didn't say what part of the original problem
he was changing in order to introduce his new condiditon,
_correctly_ leading he Me-109. Maybe he didn't realize
there was an incompatibility, or mybe he thought it
would be obvious which statement he was dropping.

Which just serves to demonstrate the conventional wisdom
about assumptions.

--

FF

"Rich S." wrote in message ...
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.


OK, more questions. What was the muzzle velocity of the .50 machine guns used as tail guns? What kind of gun was
installed in the stinger on a B-58?