Newsgroups: rec.sport.cricket
Subject: Re: AERODYNAMICS OF THE CRICKET BALL - scientific
From: shariq@charlie.usd.edu
Date: Tue, 22 Dec 1992 00:57:26 GMT
Reply-To: shariq@charlie.usd.edu
 <1992Dec11.061118.5360@news.clarkson.edu> <Bz9pny.Kup@sunfish.usd.edu>,<1gotmeINNp9k@csc2.anu.edu.au>
Organization: The University of South Dakota Computer Science Dept.

In article <1gotmeINNp9k@csc2.anu.edu.au>, ajc900@anusf.anu.edu.au (Andrew J Cleary) writes:
>In <Bz9pny.Kup@sunfish.usd.edu> shariq@charlie.usd.edu writes:
>
>>In article <1992Dec11.061118.5360@news.clarkson.edu>, pdy@sun.soe.clarkson.edu (Yapa,,,) writes:
>>>
>>> AERODYNAMICS OF THE CRICKET BALL  - scientific
>some interesting points deleted...
>>>
>>>It is widely believed that on damp days the ball swings more. However, the
>>>author says that there has been no scientific evidence of this. 
>>>The problem has been investigated by several researchers, but have found
>>>no significant change in pressures or forces when Rel. Humidity was changed
>>>upto 40 %.
>>>
>>>Yapa
>>>
>>>
>>>> 
>>I gues the ball will swing more on a damp day because the atmosphere is heavier
>>and and the linear motion is retarded, thus the lateral motion is enhanced. Try 
>>throwing a ball through water and you see how it moves. So I think there is
>>scientific evidence thatthe ball should move more on damper days. At least that
>>is what I think. What do you think?
>
>>Shariq
>
>A good try (this is also logic used to explain why baseballs are not hit
>as far on humid days, but it fails there too), but there is a problem with
>your water analogy. Yes, *water* is much denser than air, humid or not, and
>balls thrown underwater do some strange things. However, water is denser than
>air because it is a *liquid* as opposed to a *gas*. Intuitively we usually
>think that humid air is denser than non-humid air. However, recall from
>our school days that a molecule of a gas takes up the same amount of space
>no matter what the molecular weight is; and that the molecular weight of
>H20 is 18, while that of Oxygen is 32,
 Yes but then air is not just oxygen. It is 78% nitrogen which has a weight
 of 14 I think. There is just 20% oxygen in the air and furthermore other than
 the oxygen if there is H2O in air it is likely to retard the motion of the 
 ball with regard to thrust of liquids which are greater than that of gases so
 that is that.
>and we conclude that humid air is
>most likely *less* dense than nonhumid air. Of course it's not quite that
>simple (there are other gases in the air of course (nitrogen mainly)), but
>you see what I mean.
>
>Nonetheless, your point about the retardation of the linear motion bears
>thought, especially in combination with my comment about baseballs above.
>Another interesting point (and somewhat of a counterpoint to what I said
>above): on a humid day, is there just more H20 gas around, or are there
>actually microscopic *water* droplets floating in the air? If the latter,
>then your argument sounds much better. Perhaps some meteorologist can
>fill us in.
>-- 
>Andrew J. Cleary
>Centre for Information Science Research
>Australian National University
>acleary@thrain.anu.edu.au

Shariq

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