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"abripl" <ignord_eml@hotmail.com> wrote in message
news:1126135743.304867.120070@g44g2000cwa.googlegroups.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 do not 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.
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Re: Physics question
