Re: Here's one for Bob (hope it makes your head spin)

On Sep 7, 7:40 am, Ron Johnson <ron.l.john...@xxxxxxx> wrote:
On 09/07/07 07:10, bri...@xxxxxxxxxxxxxxxxx wrote:



In article <2t%Di.304$hP...@xxxxxxxxxxxx>, Ron Johnson <ron.l.john...@xxxxxxx> writes:
On 09/06/07 12:57, Bill Gunshannon wrote:
In article <fbpdrb$oa...@xxxxxxxxxxxxxxxxx>,
davi...@xxxxxxxxxxxxxxxx writes:
A lot of science fiction ideas may well be feasible but the method by which
they are accomplished will in the majority of cases be far different from that
envisaged by the scifi author. We went to the moon but we didn't use a cannon
like Jules Verne (though in other respects Verne was fairly accurate).
There are some who would disagree with your idea regarding wether or not
we used a cannon. Have you ever seen the quote from Chuck Yeager about
why he turned down the opportunity to be one of the first astronauts?
No.

But a cannon and a rocket are polar opposites. One uses fluid
dynamics and the other Newton's 3rd Law.

A cannon and a rocket are identical. Both use Newton's 3rt law.

Eh.

It's just that the one uses a somewhat larger reaction mass than
the other.

Guns use chemically unstable materials to "[produce] a sudden
expansion of the material usually accompanied by the production of
heat and large changes in pressure (and typically also a flash
and/or loud noise) upon initiation; this is called the explosion.]

The gas expanding in the confined area of the barrel "blows" the
projectile out the barrel like a breeze blows a leaf, or a person
blows a feather with his breath.

OTOH, rockets "[obtain] thrust by the reaction to the ejection of
fast moving fluid from within a rocket engine."

However... the gun's recoil is an expression of Newton's 3rd.



Newton's third law: "For every action there is an equal an opposite
reaction."

You have described actions -- chemicals exploding, gas expanding,
breeze and breath blowing -- and named the reactions to those actions.
Where is the law not applicable in any of your examples?


.

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