>> Tell me, does this mean that there's no such thing as an inelastic 
>> collission outside of textbooks?
> 
> YOu mean no such thing as an *elastic* collision?  No, not at a 
> macroscopic level.  Any collision is going to lose some energy to sound, 
> heat, plastic deformation etc, some things get pretty close though.

No, I mean... it's not "really" possible for two solid objects to hit 
each other without deforming at all.

-- 
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*

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Orchid XP v8 wrote:
> Well, I mean, there's only, what, 50 states in the USA? Given that my 
> company has 3 sites over there, *somebody* is bound to be in the same 
> state as one of them! ;-)

I dunno. My wife grew up in China, like a billion others, and she's 
constantly running into old school buddies and such. I'm saying every couple 
of months we find out someone she went to high school with on the other side 
of the world either works down the hall, lives down the street, .....

It's kind of freaky.

One day shortly after we moved in, she looks out the window during breakfast 
at the neighbor's yard and says "I think his name is Jeff. He was at a 
conference I went to in New York."  And it was.

Very long-tail.

-- 
   Darren New, San Diego CA, USA (PST)
   "Ouch ouch ouch!"
   "What's wrong? Noodles too hot?"
   "No, I have Chopstick Tunnel Syndrome."

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Orchid XP v8 wrote:
> No, I mean... it's not "really" possible for two solid objects to hit 
> each other without deforming at all.

Hitting without deforming is called an elastic collision, if that's the 
confusion.

At the macroscopic level, that doesn't happen. At the quantum level, things 
don't "hit" at all. :-)

-- 
   Darren New, San Diego CA, USA (PST)
   "Ouch ouch ouch!"
   "What's wrong? Noodles too hot?"
   "No, I have Chopstick Tunnel Syndrome."

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> Hitting without deforming is called an elastic collision, if that's the 
> confusion.

Really? How bizzare...

> At the macroscopic level, that doesn't happen. At the quantum level, 
> things don't "hit" at all. :-)

As someone once said,

   "Gravity is far weaker than electromagnetism. To demonstrate this, 
consider a person jumping off the top of a tall building. It takes 60 
seconds for gravity to accelerate your body as you fall, but only 0.08 
seconds for electromagnetism to bring it to a halt at the bottom."

Mmm, messy. :-D

-- 
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*

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On Mon, 02 Feb 2009 10:23:02 +0000, Invisible wrote:

> scott wrote:
> 
>> Hehe I laughed when I saw the bbc website too, with it's "Heavy Snow"
>> shock-headline, only to be followed by photos like these:
>> 
>> http://newsimg.bbc.co.uk/media/images/45435000/jpg/
_45435350_006818362-1.jpg
> 
> PEOPLE OF BRITAN, THIS IS NOT WHAT HEAVY SNOW LOOKS LIKE! THIS IS A
> MINOR FLURRY. GET SOME PERSPECTIVE.

Well, one of the things that always amused me was seeing cities shut down 
down south because of a snow amount like what you got.  The thing is, all-
weather tires on cars isn't common in the southern US AFAIK, and the 
south tends not to have snow removal equipment.  Couple that with people 
who have never actually driven on anything worse than a wet, oily road 
and put them on a skating rink....it can get more dangerous than driving 
with experienced winter-weather drivers in Utah on black ice.

How much snow removal equipment is there in Milton Keynes?

> Why, when I was a lad (no! come back!), my old man used to drag me and
> my little sister up to the top of the hill, and then she'd sledge to the
> bottom again. And let me tell you, I can remember walking in snow *so
> deep* that I'd be up to my knees in it, and it all used to fall in the
> top of my boots! :-P
> 
> OK, my boots were probably only a foot high or so, but still... the snow
> used to lay for *weeks* on end, not an hour or two. Hell, as recently as
> 1996 I remember us getting about 20 cm of snow, and nobody seemed that
> bothered about it.
> 
>> What on Earth would the headline be if there was actually, you know,
>> about 30cm of snow?
> 
> God only knows... :-D
> 
> I'm still unimpressed by the pictures of the "blizzard conditions"
> featuring a bunch of people trying to push a car out of the ankle-deep
> snow. I mean, why are cars spinning their wheels in 1.5 cm of snow??
> There was more snow than that in my estate, and nobody appeared to have
> any trouble with it...
> 
> OOC, how much snow is there in the various other parts of the world
> where POVers are reading this??

Well, I grew up in Minnesota and spent Christmases in Chicago when I was 
a kid; I learned to drive on packed snow and ice, so there isn't much 
that bothers me to drive on, even black ice (though obviously not my 
first choice of road surface because that stuff is incredibly dangerous).

We've got maybe 3" of snow on the ground right now here in Salt Lake 
City.  Up in the mountains, though, there will be more than a hundred 
inches of snow by now.  For example, Alta, a place my wife and I like to 
hike during the sunner, has 101" of snow right now.

But Alta is also at an altitude of 9,664 feet ASL.

Jim

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On Mon, 02 Feb 2009 09:47:13 -0800, Darren New wrote:

> It's kind of freaky.

Yeah, that is kinda weird.  I've had similar experiences - a few years 
ago, I ran into a friend of mine of many years at the airport in 
Columbus, OH.  He lives in Texas and I live in Utah.  I had left my 
sunglasses in the rental car and went back to get them, and when I got 
back into the terminal, he was literally standing behind me on the 
escalator into the terminal, and he recognised me from behind and said 
"Jim, what brings you to Columbus?"

Then I ran into another long-time acquaintance getting on board the 
connecting flight out of Cincinatti.  That was funny because we instantly 
recognised each other, but couldn't remember each others' names.

Jim

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Jim Henderson wrote:

> Well, one of the things that always amused me was seeing cities shut down 
> down south because of a snow amount like what you got.  The thing is, all-
> weather tires on cars isn't common in the southern US AFAIK, and the 
> south tends not to have snow removal equipment.  Couple that with people 
> who have never actually driven on anything worse than a wet, oily road 
> and put them on a skating rink....it can get more dangerous than driving 
> with experienced winter-weather drivers in Utah on black ice.
> 
> How much snow removal equipment is there in Milton Keynes?

Well, since yesterday every single main road in the city has been 
gritted, and even some of the minor estate roads. It's still snowing 
right now, and yet there's no snow laying on any of the road surfaces 
yet except *right* outside my front door. That can't be too bad, eh?

(Milton Keynes is arranged in a grid of roads, so saying that the main 
roads are gritted means that you can basically get between any two 
points in the city easily.)

Many of the roads outside the city aren't so clear, but so far today I 
haven't seen anything that I'd remotely consider "dangerous". Now, if 
this lot melts and then freezes again over night, *then* we'll have a 
problem...

-- 
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*

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On Mon, 02 Feb 2009 13:18:41 +0000, Invisible wrote:

> scott wrote:
>>>> BTW ABS doesn't work below about 5 or 10 mph...
>>>
>>> Really?
>>>
>>> Any specific reason?
>> 
>> I imagine it's because if the ABS system sees all four wheels go from
>> 5mph to 0mph it can't tell whether you've actually come to a stop or
>> you are skidding on ice.  At 50mph it's obvious if the wheels all stop
>> within a fraction of a second you are skidding, at low speeds it's not
>> so easy to work out.
> 
> Mmm, OK.
> 
> I must admit, I've always wondered how the hell ABS actually works.

http://auto.howstuffworks.com/auto-parts/brakes/brake-types/anti-lock-
brake.htm

> But not as much as power steering. This, as far as I can tell, should be
> logically impossible. And yet it apparently works. How baffling!

http://auto.howstuffworks.com/steering4.htm

Jim

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Orchid XP v8 wrote:
>> Hitting without deforming is called an elastic collision, if that's 
>> the confusion.
> 
> Really? How bizzare...

Because the objects hit, deform, spring apart, and then return to their 
original shapes. Like stretching elastic, you see, compared to stretching 
noodles or something.

>   "Gravity is far weaker than electromagnetism. To demonstrate this, 
> consider a person jumping off the top of a tall building. It takes 60 
> seconds for gravity to accelerate your body as you fall, but only 0.08 
> seconds for electromagnetism to bring it to a halt at the bottom."

That's a good one.

-- 
   Darren New, San Diego CA, USA (PST)
   "Ouch ouch ouch!"
   "What's wrong? Noodles too hot?"
   "No, I have Chopstick Tunnel Syndrome."

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Darren New wrote:
> Orchid XP v8 wrote:
>>> Hitting without deforming is called an elastic collision, if that's 
>>> the confusion.
>>
>> Really? How bizzare...
> 
> Because the objects hit, deform, spring apart, and then return to their 
> original shapes. Like stretching elastic, you see, compared to 
> stretching noodles or something.

I would have through elastic would mean the objects deformed, and 
inelastic would mean they didn't deform, but hey...

>>   "Gravity is far weaker than electromagnetism. To demonstrate this, 
>> consider a person jumping off the top of a tall building. It takes 60 
>> seconds for gravity to accelerate your body as you fall, but only 0.08 
>> seconds for electromagnetism to bring it to a halt at the bottom."
> 
> That's a good one.

Horizon. ;-)

-- 
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*

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