Re: [Phys-l] Final velocity of bullets

[Bernard Cleyet <bernardcleyet@redshift.com>]

I'm not surprised you couldn't get it to fall edge down.  Lotsa studies 
on falling cards beginning? by Maxwell:

http://72.14.203.104/search?q=cache:ofBBbAl1BVYJ:www.deas.harvard.edu/softmat/downloads/pre2000-05.pdf+falling+OR+fall+card+flat+physics&hl=en&gl=us&ct=clnk&cd=4 
<http://72.14.203.104/search?q=cache:ofBBbAl1BVYJ:www.deas.harvard.edu/softmat/downloads/pre2000-05.pdf+falling+OR+fall+card+flat+physics&hl=en&gl=us&ct=clnk&cd=4>

As I mentioned before, I suspect tumbling or fluttering reduces the 
terminal speed.

Cornell to the rescue:

http://www.news.cornell.edu/releases/Oct04/falling_paper.hrs.html

excerpts:

Wang and Pesavento also showed that the falling-paper effect is almost 
twice as effective for slowing an object's descent, compared with the 
parachute effect (that is, if an object falls straight down). And that 
evidently benefits trees and other plants that need to disperse seeds 
some distance from the point of origin. Plants with flattened seedpods 
also take advantage of the falling-paper effect.

and:

Wang and Pesavento also showed that the falling-paper effect is almost 
twice as effective for slowing an object's descent, compared with the 
parachute effect (that is, if an object falls straight down). And that 
evidently benefits trees and other plants that need to disperse seeds 
some distance from the point of origin. Plants with flattened seedpods 
also take advantage of the falling-paper effect.

bc, who remembers the article in TPT, Nov. '04

p.s. here's a cleyet's mom myth?  She told the storey of a stage hand 
who leaned over and his pencil fell -- here memory fails; the point is 
it penetrated the wooden stage floor.  Anyone heard this one?


Edmiston, Mike wrote:

> Now that we are finally trying to deal with the type of physics intended
> by the original post, I can tell you  the results of some experiments my
> friends and I did when I was in grad school.  We were not working with
> the bullet fired in the air problem; rather, we were working with the
> penny dropped off the Empire State Building problem.  It is still
> commonly stated that if a penny were dropped from the Empire State
> Building and it were to land on a person's head, it would kill the
> person.  Sometimes the myth even states the penny will penetrate clear
> through the person.
>
> The bullet and penny problem are essentially the same... What is the
> likely terminal velocity of a falling penny (or bullet).
>
> One source of this penny claim is when someone with a little physics
> knowledge calculates the velocity at which a penny will land if it has
> acceleration g all the way from release to landing.  Of course this is
> not true because of air friction.  Some who try to include air friction
> assume the penny falls edgewise because that presents the least air
> friction and they assume the penny will assume that orientation as it
> falls.
>
>  
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> We were never able to get a penny to fall edgewise.  It very quickly
> tumbles, and it tumbles rapidly.  It's terminal velocity is very slow,
> about 15 mph, roughly 20 ft/s, roughly 6 m/s.  I can ride my bike that
> fast.  At that time a penny was copper.  Today with copper-coated zinc
> pennies I presume the terminal velocity is lower yet.  Anyway, a penny
> dropped from a high place is not going to kill someone.
>
>  
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