[meteorite-list] Physics Questions (Having to Do, Theoretically, with Bolide Trajectories)

From: Peter Scherff <PeterScherff_at_meteoritecentral.com>
Date: Wed, 6 Mar 2013 17:12:31 -0500
Message-ID: <005a01ce1ab7$b2e5e030$18b1a090$_at_rcn.com>

Hi Michael,

Yes, that is why I posted it. In a vacuum all objects, in effect, have the
same aerodynamic property.

Peter Scherff


-----Original Message-----
From: meteorite-list-bounces at meteoritecentral.com
[mailto:meteorite-list-bounces at meteoritecentral.com] On Behalf Of Michael
Mulgrew
Sent: Wednesday, March 06, 2013 5:07 PM
To: Peter Scherff
Cc: Meteorite List
Subject: Re: [meteorite-list] Physics Questions (Having to Do,
Theoretically, with Bolide Trajectories)

Peter, that's because of the lack of atmosphere on the moon. Again (and
supported by the example you cited), mass has no effect on an object's
acceleration in free fall.

Michael in so. Cal.

On Wed, Mar 6, 2013 at 1:59 PM, Peter Scherff <PeterScherff at rcn.com> wrote:
> One of the best science for the masses demonstration ever was done on
> the Moon. Drop a hammer and a feather and what happens?
> http://nssdc.gsfc.nasa.gov/planetary/lunar/apollo_15_feather_drop.html
>
> Peter
>
>
> -----Original Message-----
> From: meteorite-list-bounces at meteoritecentral.com
> [mailto:meteorite-list-bounces at meteoritecentral.com] On Behalf Of
> Michael Mulgrew
> Sent: Wednesday, March 06, 2013 4:49 PM
> To: Meteorite List
> Subject: Re: [meteorite-list] Physics Questions (Having to Do,
> Theoretically, with Bolide Trajectories)
>
> Peter, when an object is dropped from rest on Earth its mass has
> nothing to do with its acceleration. Drop two objects of differing
> mass (but similar aerodynamic properties) and they'll both hit the
> ground at the same time; this is physics 101. I didn't read past that
> part of your post because I figured the rest of whatever you were
> trying to reason out would be flawed since your initial understandings
were in error.
>
> Michael in so. Cal.
>
> On Wed, Mar 6, 2013 at 1:37 PM, Peter Richards <pedrichards at gmail.com>
> wrote:
>>
>> To preface this, I'll let you know: I have dealt with some
>> persons who such questions have been, rather, "over the head of,"
>> (pun not intended)... one of whom seemed to settle on the theory that
>> I must be hurting my brain with too much thinking, and another who
>> was satisfied with a conclusion to a variation of the forthcoming
>> problem based on the idea that sand blows to the northeast U.S. from
>> the "midwest" region, while larger stones do not (not that these
>> persons are professional physicists, thankfully). Maybe this would be
>> better directed at a physicist, but since I am dealing with something
>> which pertains to meteorites, and certain specific falls, I will
>> submit this for consideration by the members of this list:
>> On earth, acceleration of a suspended, then falling, or
>> dropped, object, such as from a standstill, is determined by the mass
>> of the object in a positive respect and the factor of air resistance
>> in a negative respect; hence, a denser material of the same shape and
>> orientation falls faster. This is because, here on earth, we have
>> both an atmosphere, and a specific directional pull of gravity. I've
>> read that, on the moon, where resistance of the atmosphere is
>> negligible, if not absolutely nil, two objects of unlike densities
>> will be pulled downwards at an equal rate (they say, even an elephant
>> and feather will be pulled downward at the same rate, only being
>> resisted by gravitational pull from other objects in the universe, I
>> figure). If those observations are correct (and I'm not entirely sure
>> they, although, it seems as if they very well may be, to me), then
>> we've identified two situations, 1. one in which mass and density
>> with relation to shape/and orientation does matter, but sum
>> shape/volume (short for what determines air resistance) does not, for
>> if an object is twice the size of the other, although not twice as
>> dense, but an equal density, and shape, and orientation, it will fall
>> at the same rate, because the ratio between its own mass and
>> air-displacing profile is equal (I am not saying this law is
>> universal, at all scales, but for practical purposes maybe it is?),
>> and 2. another, in which, shape and orientation don't matter, and nor
>> does the mass, or the density .
>> So, finally, my question is this: Do we have a third situation
>> in which mass and density has a negligible effect, but air resistance
>> due to shape and orientation does (That is to say, compensating for
>> gravitational pull correlating to mass, or in a vector in which this
>> is negated, the objects would encounter particles travelling at
>> them.)? Again, it's somewhat difficult to imagine, but if there were
>> such a scenario, would a large heavy object, NOT be held more still
>> than a proportionally lighter and smaller object, but RATHER less so?
>> Hence, for a fourth time, would higher inertia be totally detached
>> from correlating to higher mass, thus correlating only with lower air
>> resistance, ie better aerodynamics?
>> One might think that a bolide does not fit these criteria (or
>> support this thesis), since the larger, generally less aerodynamic
>> pieces tend to travel farthest, but is this not a result of these
>> particles having been subject to less air resistance, in sum, than
>> the smaller particles, which had broken from the outer surfaces of
>> these very objects, due to the very momentum the "main masses"
>> carried, in effect, absorbing the shock for them, somewhat (meaning
>> they it is not for lack of momentum, due to lower mass, that they end
>> up travelling less far)?
>>
>> (a question of) Peter Richards
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Received on Wed 06 Mar 2013 05:12:31 PM PST