On Jul 8, 3:21*am, riverman wrote:
On Jul 8, 6:04*am, MajorOz wrote:
On Jul 7, 4:44*pm, BJ Conner wrote:
On Jul 7, 9:57*am, MajorOz wrote:
On Jul 7, 9:28*am, BJConner wrote:
On Jul 6, 12:07*pm, MajorOz wrote:
On Jul 6, 6:15*am, riverman wrote:
On Jul 6, 5:18*am, MajorOz wrote:
On Jul 5, 7:36*pm, riverman wrote:
On Jul 5, 3:27*pm, rw wrote:
On 7/5/10 7:08 AM, rw wrote:
On 7/5/10 5:12 AM, riverman wrote:
I'm not convinced that heat expands the radius of the hole, as in a
photographic enlargement. Objects expand around their physical mass.
There is a classic physics demonstration with a steel ring and a steel
ball where you heat the ring and find that the ball will not fit
through the ring. So, just as the hole in a rising donut (or bagel is
more like it) gets smaller, I would expect the hole to get smaller if
you heated the female section. But countereffecting that would be that
the circumference of the torus would also increase. Maybe there is
some sort of ratio of circumference to torus thickness where the hole
actually does not change....I don't know. But the action of the female
end of a ferrule is a very thought-provoking thing.
http://physics.bu.edu/~duffy/py105/Temperature.html
BTW, I think you're misremembering the ring and ball experiment. It
actually demonstrates just what I (and others) have been saying about
thermal expansion of a hole.
--
Cut "to the chase" for my email address.
You're right. I just saw this on youTubehttp://www.youtube.com/watch?v=V0ETKRz2UCA
So OK, *the hole gets bigger when the female end is heated, however
the male end gets bigger also. Which gets bigger faster?
Read my post. *It explains what and why.
oz
Err, which one, Oz? The one where it says "can't guarantee anything,
but that is the theory" or the one that says "disregard my response"?
:-)
--riverman
They are both sincere (in context), but the one I had in mind was that
the metal will expand or contract with temperature change based on the
original (pick your starting point) temp.
However, they all will change at percentage of the starting size
(assuming identical composition).
To wit: if expansion is X %, a three inch circle will expand to 3 in
+ *X% of three inches, while the little bit less than three inches
will expand to LBLT3in. + X% of LBLT3in, resulting in an ever widening
gap as temp increases.
In sum: the gap between inside and outside widens with increasing
temperature.
Ideally, of course, fill the (hopefully) hollow inside one with water,
freeze the whole mess, then zap the outside QUICKLY with heat and slip
them apart. Kinda like baked Alaska.
Works only with metal. *Obviously not with graphite.
In a sever case in the past of irretrievably stuck graphite ferrules,
I just wound up with a rod five inches shorter.
( Solution left as an exercise -- hint: it involved a jeweler's saw )
cheers
oz- Hide quoted text -
- Show quoted text -
"In sum: the gap between inside and outside widens with increasing
temperature. "
Maby it does in the Russian navy but not anywhere else in the world.
Although I have been aboard Russian (actually Soviet) ships, my
engineering degrees are from US schools.
Maby (sic) your experience is different ?
cheers
oz- Hide quoted text -
- Show quoted text -
Your right. *I was thinking about trigger guard assemblies or
something.
I had to go back and thing about a sections of RR track- one 100' long
and one 101' . * *The units of change are in/in/degree IF you bend
them into circles the circumference of the bigger circle grows more
and the radius becomes greater.
.
There is the old chestnut about a metal strap around a barrel. *Cut
the strap and insert a piece 10 ft long and then re-make it into a
circle. *Lay it down, so that the barrel is centered in the "hoop".
Distance between barrel and hoop is a bit over 19 inches.
Now put a metal strap around the earth. *Increase, as above, the
length by 10 feet.
How "high" above the ground will it then be ? * * * * As before, about
19 inches.
Around a marble? *19 inches.
Irritating, but that's the way it is.
cheers
oz
My favorite version of that goes the other way; how much do you have
to add to a strap that surrounds the earth in order to raise it one
inch off the ground? Turns out that its the same amount you have to
add to your belt if you need to wrap it around a jacket that is one
inch thick, or around the universe if it grows one inch in radius.
--riverman
Brings to mind an interesting illustration I encountered recently in a
book, a compendium of mathematical oddities, puzzles, trivia, etc.
Evidently there is a highway that circles greater London. Don't
remember exactly how long it is but I think it's 85 kilometers or
thereabouts. In any case, as posited in the problem, there are two
lanes in each direction. The question is how much distance (and thus
how much time) can be saved by driving the entire cicuit in the inside
lane as opposed to the outside lane, assuming the the lanes are each x
feet (or whatever other unit of measurement one prefers) in width.
Counterintuitively, the answer turns out to be something
minuscule.....pi times the difference in radius, the latter value
being something on the order of 5 or 6 yards. Surprising to those of
us (the vast majority) who don't spend our lives immersed in
mathematics to the exclusion of a world full of vastly more important
and intersting stuff, but not hard to grasp for those of us (a
minority, if personal experience is any guide) familar with the
rudiments of euclidian geometry. The bottom line is that it obviously
isn't worth the bother to stay in the inside lane.
However.....
The shortest path between two points is a straight line.....nevermind
astrophysics, non-euclidian spaces, Eisteinian relativity and all
that.....we're talking about getting from here to there on the surface
of good old terra firma via automobile here. Of course much more
often than not there is no straight line from here to there over any
appreciable distance. The question that arises is whether or not it's
worth the bother to pursue the closest approximation to a straight
line that is possible on a given route. That is to say, over the
course of, say, a thousand mile cross-country trip, is there a
substantial savings in mileage and time to be gained by taking the
inside lane in each curve, switching lanes as necessary and taking the
shortest, straightest path possible between successive curves?
Don't know. On the face of it, it appears that no simple equation (as
in the original problem) is going to answer the question. Too much
appears to depend on the number, shape, radii and length of the
curves, as well as their spacing, which is to say, the lengths of the
straight stretches between them.
Personally, I've always felt that where consistent with safe driving
it can't hurt to try, and have made an occasional practice of it,
although I've never conducted anything approaching a rigorous
experiment.
giles