ins_apmj@jhunix.UUCP (Patrick M Juola) (11/07/85)
In article <668@petrus.UUCP> mwg@petrus.UUCP (Mark Garrett) writes: >Somebody here said they saw a film about the Lindburg flight where old >CL was flying along, bored, and noticed a fly inside the plane. He >started wondering if the mass of the fly contributed to the weight >of the plane. If the fly is sitting on something then obviously it does. >But what if the fly is flying around? What if the fly is falling? Does it >make a difference if the plane is airtight or not? > If the fly is flying horizontally, then it's still sitting on something, right? It's sitting on air columms that transmit the pressure downward (fluid dynamics or something like that). If the plane is airtight, then the columns terminate against the floor of the plane, so the weight of the fly is pressing down on thefloor. (i.e. Yes, it does contribute.) If the plane is NOT airtight, then the columns may or may not terminate against the floor, so it would not increasethe planes weight by as much, the exact amount depending on the degree of airtightness. ("Degree of airtightness"???? Did I really type that!?) If the fly is climbing, then the columns are not only supporting the weight, butthe reaction force necessary to climb, so the added weight increases. On the other hand, if the fly is in free fall, then the columns are supporting no weight at all and the plane's weight is unchanged. I hope this clears it up -- any questions? any flames? any cute girls who want my phone #? :-) Pat Juola Johns Hopkins Univ. Dept of Maths