bobp@petfe.UUCP (Bob Philhower) (08/28/85)
<<>> OK, all you bird-lovers (P?); anyone want to comment on this situation? Given: A bottle, (of arbitrary size), containing one (1) bird (of arbitrary species). The bottle is placed on a garden-variety bathroom scale (arbitrarily accurate), and the weight of the system is measured with the bird sitting on the bottom of the *closed* bottle. Now the bird decides to fly around inside the bottle, and the weight is read again. Any weight difference? Now, what if the bottle cap (massless, of course) is removed; again, any weight difference? What happens as the bird flies to the top of, and eventually out of, the bottle? We've tried this, but after squeezing a robin through the bottle neck, it doesn't seem to want to fly. -dan-
cjh@petsd.UUCP (Chris Henrich) (08/28/85)
[] In article <457@petfe.UUCP> bobp@petfe.UUCP (Bob Philhower) writes: >Given: A bottle, (of arbitrary size), containing one (1) bird >(of arbitrary species). The bottle is placed on a garden-variety >bathroom scale (arbitrarily accurate), and the weight of the system >is measured with the bird sitting on the bottom of the *closed* >bottle. Now the bird decides to fly around inside the bottle, and >the weight is read again. Any weight difference? > >Now, what if the bottle cap (massless, of course) is removed; again, >any weight difference? What happens as the bird flies to the top of, >and eventually out of, the bottle? While the bird is flying around in the bottle, it has to move its wings in such a way that there is more pressure on their bottom surfaces than on their tops. A side effect is that air currents are created which cause increased pressure on the bottom of the bottle. Thus the bird's weight affects the scale exactly as if it was sitting on the bottom of the bottle. When the air inside the bottle is no longer isolated from the air outside, the forces do not necessarily balance. It seems likely to me, however, that little change or none will be caused by just opening the top of the bottle. When the bird flies out of the bottle, the downward push that it exerts on the air will not register on the scale, but rather will act on the floor or other surroundings. So the weight reading decreases. This is not exactly intuitive, because the pattern of forces is complex. But if you *really* *believe* that Newton's third law applies to each little piece of the complex pattern, then you can expect it to apply to the aggregate of them. Regards, Chris -- Full-Name: Christopher J. Henrich UUCP: ..!(cornell | ariel | ukc | houxz)!vax135!petsd!cjh US Mail: MS 313; Perkin-Elmer; 106 Apple St; Tinton Falls, NJ 07724 Phone: (201) 758-7288
rdp@teddy.UUCP (08/28/85)
In article <457@petfe.UUCP> bobp@petfe.UUCP (Bob Philhower) writes: ><<>> >OK, all you bird-lovers (P?); anyone want to comment on this situation? > >Given: A bottle, (of arbitrary size), containing one (1) bird >(of arbitrary species). The bottle is placed on a garden-variety >bathroom scale (arbitrarily accurate), and the weight of the system >is measured with the bird sitting on the bottom of the *closed* >bottle. Now the bird decides to fly around inside the bottle, and >the weight is read again. Any weight difference? > A similar puzzler was given in an old Scientific American (maybe 20 years ago). Seems there was this guy with a panel truck filled with pigeons. He comes to a rickety old bridge, gets out, and starts banging on the side of the truck. A local farmer is watching this spectacle and asks the driver why he is doing this. The driver responds "Because I don't think the bridge will support both my truck and the birds, so I want to get the birds flying around while I drive over". The question is, will the birds flying around make any difference. The answer is, in an airtight, or nearly airtight container (truck, bottle, etc.) there will be no difference. Why? because the birds exert a downwards force equal to their mass times the acceleration of gravity. This force is the same whether they are sitting or flying. In the former case, that force is counteracted by the bed of the truck(or the bottom of the bottle). In the latter case, the counter-acting force is supplied by the air, and in turn, by the bed of the truck (etc.). There will be no difference in average weight (I say AVERAGE, because there may be slight differences when the birds move up or down). >Now, what if the bottle cap (massless, of course) is removed; again, >any weight difference? What happens as the bird flies to the top of, >and eventually out of, the bottle? > >We've tried this, but after squeezing a robin through the bottle neck, >it doesn't seem to want to fly. > Try bees! Or mayonnaise jars for the bird!
john@frog.UUCP (John Woods) (08/29/85)
> In article <457@petfe.UUCP> bobp@petfe.UUCP (Bob Philhower) writes: > ><<>> > >OK, all you bird-lovers (P?); anyone want to comment on this situation? > > > >Given: A bottle, (of arbitrary size), containing one (1) bird > > Answer... > > > >We've tried this, but after squeezing a robin through the bottle neck, > >it doesn't seem to want to fly. > > > Try bees! Or mayonnaise jars for the bird! > I tried a mayonnaise jar, but it didn't want to fly either! -- John Woods, Charles River Data Systems, Framingham MA, (617) 626-1101 ...!decvax!frog!john, ...!mit-eddie!jfw, jfw%mit-ccc@MIT-XX.ARPA You have violated Robots Rules of Order, and will be asked to leave The Future!
dgary@ecsvax.UUCP (D Gary Grady) (08/29/85)
In article <457@petfe.UUCP> bobp@petfe.UUCP (Bob Philhower) writes: > Given: A bottle, (of arbitrary size), containing one (1) bird > (of arbitrary species). The bottle is placed on a garden-variety > bathroom scale (arbitrarily accurate) [...] ... and we're asked if the reading on the scale depends upon whether the bird is flying and whether the bottle is open. I'll add a question: if it makes no difference, does the weight on a scale increase because a bird (or a plane, or, for that matter, Superman) flies overhead? This question is the basis for a bizarre joke about somebody delivering 3 tons of parakeets in a 1-ton truck, and having to pound on the wall behind him "to keep 2/3 of them in the air." Jack Paar told it on the Tonight Show and Hugh Downs, his announcer, stopped the show dead by explaining that 3 tons of parakeets could not possibly fit into a panel truck (Downs must have a physics degree... or maybe even something worse, like math). As for me, every morning I get on my bathroom scale with my parakeet, Braak, standing on my finger. If the reading is greater than that for the previous day, I give Braak hell. Yes, I know this isn't physics. Turn off those accelerators. -- D Gary Grady Duke U Comp Center, Durham, NC 27706 (919) 684-3695 USENET: {seismo,decvax,ihnp4,akgua,etc.}!mcnc!ecsvax!dgary
douglas@cxsea.UUCP (Douglas Wells) (08/29/85)
> [] > In article <457@petfe.UUCP> bobp@petfe.UUCP (Bob Philhower) writes: > >Given: A bottle, (of arbitrary size), containing one (1) bird ... > >and eventually out of, the bottle? > [Christopher J. Henrich - replies] > While the bird is flying around in the bottle, it has ... > pattern, then you can expect it to apply to the aggregate of > them. Consider the following reductio ad absurdam, and I think the answer becomes obvious. Allow the opening to the bottle to become infinitely large. ================================================================== Independent Truckers - The last American Cowboys Douglas
hull@hao.UUCP (Howard Hull) (08/31/85)
> I tried a mayonnaise jar, but it didn't want to fly either! > ...!decvax!frog!john, ...!mit-eddie!jfw, jfw%mit-ccc@MIT-XX.ARPA I tried a mayonnaise jar, too, but the dadgum bird got away, and now there's mayonnaise all over the &%$#"! place. Bartholomew
rdp@teddy.UUCP (09/03/85)
In article <313@cxsea.UUCP> douglas@cxsea.UUCP (Douglas Wells) writes: >> [] >> In article <457@petfe.UUCP> bobp@petfe.UUCP (Bob Philhower) writes: >> >Given: A bottle, (of arbitrary size), containing one (1) bird > ... >> >and eventually out of, the bottle? >> >[Christopher J. Henrich - replies] >> While the bird is flying around in the bottle, it has > ... >> pattern, then you can expect it to apply to the aggregate of >> them. > >Consider the following reductio ad absurdam, and I think the answer >becomes obvious. > >Allow the opening to the bottle to become infinitely large. > I tried doing that, and the thing got so heavy it broke by bathroom scale.