From: mwsn_ss@uhura.cc.rochester.edu (Matthew Weasner)
Newsgroups: alt.satanism,alt.atheism,soc.motss,sci.physics,alt.religion.emacs,talk.religion.newage,alt.pagan,alt.sex,talk.religion.misc
Subject: Re: Subject?
Date: 11 Sep 92 00:19:18 GMT
Organization: University of Rochester (Rochester, NY)

In article <1992Sep04.044103.6779@cubic.com> hees@cubic.com (Phil Hees) writes:
>
>I can't believe I'm posting a physics flame in alt.sex... :)
>
>
>In article <25832@dog.ee.lbl.gov> sichase@csa1.lbl.gov writes:
>>In article <1992Aug28.134921.28421@galileo.cc.rochester.edu>, mwsn_ss@uhura.cc.rochester.edu (Matthew Weasner) writes...
>>>In article <25660@dog.ee.lbl.gov> sichase@csa3.lbl.gov writes:
>>>>In article <34544@cbmvax.commodore.com>, kominetz@cbmvax.commodore.com (John Kominetz - CATS) writes...
>>>>>Bush spends.
>>>>>-- 
>>>>>                                      __
>>>>>        John Kominetz, III            \/          Aikido Ki No Kawa
>>>>>  Commodore Apps and Tech Support           "I speak for myself, not C=."
>>>>> ========================================================================
>>>>>  "The higher you fly, the faster you fall."          -- Laurie Anderson
>>>>
>>>>    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>>>>
>>>>That's not true.  You have a defective .sig.
>>>>
>>>>-Scott
>>>actually, in a way, I think it is true. You accelerate at the same rate. 
>>>(9.8 m/s ?) So if you are higher, you get more time to accelerate. Therefore,
>>>you are going faster when you hit the ground and go <SPLAT!>. Elementary, my
>>>dear Scott. What does Aikido Ki No Kawa mean anyway?
>>> 
>>>my 2 measly cents.
>>
>>Listen up, Sherlock. :-)
>
>
>OK, Scott, since you keep going out of your way to pick on people
>(first John and then Matthew), I'm going to have to pick on you. :)
>
>
>>When an object falls through the atmosphere (which is what happens if
>>it suddenly stop flying) it achieves terminal velocity very quickly.
>>The actual value of this terminal velocity varies depending upon the
>>object's shape -
>          ^^^^^
>
>Actually, it depends on size, shape, surface characteristics, and mass.
>A few comments:
>
>Terminal velocity is the velocity at which the force due to drag equals
>the force due to gravitational attraction.  The calculation of terminal
>velocity is not an easy problem, as any student of fluid dynamics knows:
>there are three different formulae for drag depending on whether the
>speed is in the slow, turbulent or supersonic range.
>
>Saying that "the actual value of this terminal velocity varies depending
>upon the object's shape" is very misleading.  For example, in a fluid
>medium such as the atmosphere, a lead sphere will fall faster and reach
>a higher terminal velocity than a styrofoam sphere of the same shape and
>size.  Also, a large styrofoam sphere will fall faster than a small
>styrofoam sphere (despite what Galileo said) because drag is
>proportional to the square of the radius, while mass (and therefore the
>force due to gravitational attraction) is proportional to the cube of
>the radius.  Surprisingly, a roughly textured object may or may not fall
>faster than a smooth textured object: normally the roughness will
>increase drag, but in some cases the roughness may act to reduce the
>onset of turbulent flow, decreasing drag.  This is one of the reasons
>that wind tunnel testing is so important.
>
>BTW, Galileo's experiment worked because the ratio of the drag force to
>the gravitational force is very small for a cannonball moving at less
>than 100 m/s.
>
>
>> - but for a person it is probably in the vacinity of 60 - 200 mph
>>(someone else may have better information - I'm sure that parachuters
>>know a better value)
>
>An experienced skydiver can vary her body orientation (varying drag) to
>speed or slow her rate of descent over a considerable range.  Your
>values are approximately correct for a human body, although I think that
>your lower limit is too low.  However, who said we were talking about a
>person?  "The higher you fly, the faster you fall" - kind of general,
>isn't it?  Different terminal velocities for airplane, helicopter, bald
>eagle, Goodyear Blimp, etc. :)
>
>Also, you misspelled vicinity.  (Usenet guidelines be damned... I _like_
>spelling flames!)
>
>>at 9.8 m/s^2 (note the units - yours were wrong) you get to terminal
>>velocity in 3 seconds (for 60 mph.)
>
>Actually 2.7 seconds, although you are correct if you were limiting it
>to one significant digit.
>
>>In that time you drop only 30 meters.
>
>44.1 meters using your figure of 3 seconds, 36.5 using my figure of 2.7
>(distance = 0.5 * a * t^2).  I expected better math from someone at
>Lawrence Berkeley Laboratory. :)
>
>But actually, you don't just accelerate at a constant 9.8 m/s^2 until
>you hit terminal velocity and then suddenly stop accelerating.  At any
>instant, your acceleration can be calculated as (Fg - Fd)/m, where Fg is
>the force due to gravitational attraction, Fd is the drag force, and m
>is the mass of the object.  Fd increases with increasing velocity but
>the relationship is very nonlinear, particularly at the onset of
>turbulent flow.  As a first (very rough) approximation, I get:
>
>  after 1 second       31% of terminal velocity (using 60 MPH figure)
>  after 2 ...          52%
>        3              67%
>        4              77%
>        5              84%
>  after 6.2 seconds    90% of terminal velocity
>  after 8.1 seconds    95% of terminal velocity
>
>the last two entries being commonly used endpoints.  So for your basic
>falling person it will take somewhat more than your 3 seconds to get to
>something which we could reasonably call "terminal velocity".
>
>>So if you are falling from any height much greater than 30 meters
>>(probable if you were flying,) then you will reach terminal velocity
>>early in your fall.
>
>Again, you never "reach" terminal velocity.  It is more meaningful to
>talk about reaching a value such as 90% of terminal velocity.  Granted,
>this is nitpicking... :)
>
>>The velocity with which you splat will therefore be independent of the
>>height from which you fell.
>>
>>-Scott
>
>Your conclusion is essentially correct, despite my nitpicking.  But
>returning to the original quote, I would like to cite two good points
>from Steve Franklin's post in this thread:
>
>	Well, if you guys really want to know the answer - the air is
>	thinner at higher altitudes, and because of this, the terminal
>	velocity is higher in the upper reaches of the atmosphere. Thus,
>	the higher you fly, the faster you will fall, but your terminal
>	velocity will decrease as you continue to fall...
>
>In this context, the original .sig was truthful.  It would also be
>truthful if the falling object were sufficiently large and/or dense
>that it never reached terminal velocity in the finite falling distance
>that the Earth's atmosphere represents.  (Oh, the original quote didn't
>specify the Earth... no terminal velocity on the Moon, is there? :)
>
>	However, I personally think the initial statement is
>	metaphorical to the use of drugs. I don't think it has anything
>	to do with parachuting or free-fall.
>
>It could also be metaphorical to political careers, showbusiness careers
>or the career of Donald Trump.  In any case, considering the source of
>the quote it was surely a metaphor.  Don't listen to much Laurie
>Anderson, do you?  :)
>
>--
>Phil Hees
>hees@cubic.com
>"The higher you fly, the faster you fall."          -- Laurie Anderson

gee thanks Phil. my hero! hee hee. :-)

matt.