Yesterday my mum notified me of the "blizzard" outside. This consisted 
of approximately 3 tiny snowflakes barely visible to the naked eye.

Yesterday evening, the ground was about 20% covered in whiteness. If you 
imagine taking a chocolate cake and lightly sprinkling it with icing 
sugar, that's roughly what it looked like. (For extra points... go *get* 
a chocolate cake and eat it!)

This morning, as I walked to my car there was approximately 15 mm of 
snow laying on the ground, and barely visible flakes were still 
continuing to fall. On the way to work, the snow cover gradually became 
thinner and thinner, until in Coventry there isn't even a full covering.

On the radio I hear that the MET office has issued a country-wide Severe 
Weather Warning, schools and businesses have been closed, and the 
Highways Agency has advised people not to travel "unless absolutely 
necessary".

Uh... WTF? It's not exactly like the Arctic out there! :-P

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Check it out:

http://news.bbc.co.uk/1/hi/uk/7864395.stm

Oh my God, look at that snow! It's almost *ankle high*! :-P



For referense, *this* is "heavy snow":

http://www.telenendaz.ch/documents/fond%20ecran/1024boardercross.jpg

See how the base of that tree is sunk down into the snow? There's 
because there's *multiple feet* of snow. Not this 11 mm nonesense.

Post a reply to this message

> Uh... WTF? It's not exactly like the Arctic out there! :-P

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

What on Earth would the headline be if there was actually, you know, about 
30cm of snow?

Post a reply to this message

> For referense, *this* is "heavy snow":
>
> http://www.telenendaz.ch/documents/fond%20ecran/1024boardercross.jpg
>
> See how the base of that tree is sunk down into the snow? There's because 
> there's *multiple feet* of snow. Not this 11 mm nonesense.

This too (taken from my apartment door a couple of years ago)

http://farm1.static.flickr.com/56/108046767_2e327c4fa8_o.jpg

See how the car wheels are completely under snow?

*That* is heavy snow, when you can't drive until the snow plough comes 
through (and shoves 10 tons more snow onto your car which you have to then 
spend 2 hours removing).

Here's my car a week later when I decided to eventually dig it out:

http://farm1.static.flickr.com/19/109805956_ac25f22cf5_o.jpg

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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.

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??

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scott wrote:
> This too (taken from my apartment door a couple of years ago)
> 
> http://farm1.static.flickr.com/56/108046767_2e327c4fa8_o.jpg
> 
> See how the car wheels are completely under snow?
> 
> *That* is heavy snow, when you can't drive until the snow plough comes 
> through (and shoves 10 tons more snow onto your car which you have to 
> then spend 2 hours removing).

Heeheee... Where in the world is this?

> Here's my car a week later when I decided to eventually dig it out:
> 
> http://farm1.static.flickr.com/19/109805956_ac25f22cf5_o.jpg

Indeed: The snow was there FOR A WEEK! Heh.

Post a reply to this message

> Heeheee... Where in the world is this?

Munich.

> Indeed: The snow was there FOR A WEEK! Heh.

A week?  THat year I think there was snow around until April or so.  I 
remember one day in particular where the air temperature was about 15 
degrees and sunny (it was the first spring-feeling day) and yet there were 
still big piles of snow around.

This winter we have just had 4 or 5 snowy days, each time about 5-20 cm, 
which have then melted *a bit*, but it's never really got warm enough over 
the last couple of months to melt it all away properly.

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For extra credit, play with this:

http://www.metoffice.gov.uk/climate/uk/stationdata/cambridgedata.txt

;-)

I notice that there isn't a single month since the previous millennium 
where the minimum temperature has been negative, but looking at the 
start of the listing it seems quite common.

Post a reply to this message

> For extra credit, play with this:
>
> http://www.metoffice.gov.uk/climate/uk/stationdata/cambridgedata.txt
>
> ;-)

:-)

I see that if it follows that trend, in 100 years we'll be 2.4 degrees 
warmer.  Which seems inline with what I've read elsewhere...

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Attachments:
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scott wrote:

> I see that if it follows that trend, in 100 years we'll be 2.4 degrees 
> warmer.  Which seems inline with what I've read elsewhere...

Impressive. I couldn't get my copy of Excel to graph it adaquatly; it 
just came out as a dence mass of apparently random points. (Well, it 
*is* 150 years of data...)

It appears that the winter temperatures are pretty unstable anyway. If 
you look only at the *summer* temperatures though, a clear trend seems 
visible.

I wonder if you could somehow plot this on a circular graph with a 
12-month cycle?

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http://www.metoffice.gov.uk/weather/uk/advice/snow.html

"If braking is necessary, pump the brakes don't slam them on."

...unless you have friggin ABS! :-P

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> "If braking is necessary, pump the brakes don't slam them on."
> 
> ...unless you have friggin ABS! :-P

BTW ABS doesn't work below about 5 or 10 mph...

Post a reply to this message

scott wrote:
>> "If braking is necessary, pump the brakes don't slam them on."
>>
>> ...unless you have friggin ABS! :-P
> 
> BTW ABS doesn't work below about 5 or 10 mph...

Really?

Any specific reason?

Post a reply to this message

>> 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.

Post a reply to this message

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.

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!

Post a reply to this message

Invisible wrote:
> Uh... WTF? It's not exactly like the Arctic out there! :-P

There are large numbers of people who have difficulty driving in 
anything more slippery than rain.  This is most likely in areas which 
are known for the mildness of their winters.

Add to this the general temperament of the government to view itself as 
some kind of mother to the people, and you get urgent warnings telling 
people to regard as wild uncontrollable dangers things that in fact 
present a small and manageable risk.

I grew up in Michigan, and can tell you that even as experienced with 
the snow as they are there, the first significant snowfall of the winter 
is a refresher course in winter driving for just about everybody.

Regards,
John

Post a reply to this message

> I must admit, I've always wondered how the hell ABS actually works.

A speed sensor on each wheel, if one drops too quickly compared to the 
others, or they all drop too quickly than what is "usually possible" a 
solenoid is opened that releases the brake pressure until the wheels speeds 
are back to normal, then the solenoid is closed.  The process might then 
repeat if the driver is still pressing the brake pedal hard - this is the 
"pulsing" sensation you feel.

Note that modern cars are much more complex, with ABS being part of a much 
larger control system, capable of regulating the braking force to each 
individual wheel (to allow each wheel to be giving the maximum stopping 
power, and to prevent skids, wheel-spin etc).

> 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!

There's a part in the steering system that twists or bends by a specific 
amount depending on how hard you tug at the wheel.  A set of valves then 
controls some pressurised hydraulics based on how much force you are putting 
into the wheel, which helps you steer.

Newer cars have a torque transducer and an electric motor with some clever 
software.  This saves on fuel as there is no hydraulic compressor having to 
be run the whole time (usually you only need power assist at low speeds).

Post a reply to this message

>> I must admit, I've always wondered how the hell ABS actually works.
> 
> A speed sensor on each wheel, if one drops too quickly compared to the 
> others, or they all drop too quickly than what is "usually possible" a 
> solenoid is opened that releases the brake pressure until the wheels 
> speeds are back to normal, then the solenoid is closed.  The process 
> might then repeat if the driver is still pressing the brake pedal hard - 
> this is the "pulsing" sensation you feel.
> 
> Note that modern cars are much more complex, with ABS being part of a 
> much larger control system, capable of regulating the braking force to 
> each individual wheel (to allow each wheel to be giving the maximum 
> stopping power, and to prevent skids, wheel-spin etc).

...not to mention traction control... ;-)

>> 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!
> 
> There's a part in the steering system that twists or bends by a specific 
> amount depending on how hard you tug at the wheel.  A set of valves then 
> controls some pressurised hydraulics based on how much force you are 
> putting into the wheel, which helps you steer.
> 
> Newer cars have a torque transducer and an electric motor with some 
> clever software.  This saves on fuel as there is no hydraulic compressor 
> having to be run the whole time (usually you only need power assist at 
> low speeds).

The part I can't figure out is that, as far as I can tell, hooking up a 
motor that turns the steering wheel in the same direction as you're 
trying to turn it should generate a positive feedback loop. I can't 
figure out how turning the wheel doesn't cause the powerful motors to 
rip the wheel out of your hands and put the car into full lock before 
snapping the steering column in half...

Post a reply to this message

John VanSickle wrote:
> There are large numbers of people who have difficulty driving in 
> anything more slippery than rain.  This is most likely in areas which 
> are known for the mildness of their winters.

I did notice that in the videos of people pushing cars, all the cars 
seemed to be attempting to drive uphill at no more than walking pace - 
shorly not a sensible thing to do in snow?

> Add to this the general temperament of the government to view itself as 
> some kind of mother to the people, and you get urgent warnings telling 
> people to regard as wild uncontrollable dangers things that in fact 
> present a small and manageable risk.

Yeah, maybe. I guess the government doesn't want to hear the whole "why 
didn't you warn people?" thing, or "why didn't you take action?". (OTOH, 
it didn't seem to be a problem for New Orleans...)

> I grew up in Michigan, and can tell you that even as experienced with 
> the snow as they are there, the first significant snowfall of the winter 
> is a refresher course in winter driving for just about everybody.

I can remember 1995 or so, there was a lot of snow one day. About 20 cm 
or so. Not huge, but a lot. Nobody seemed to really pay much attention. 
A few people got slightly stuck or something, but nobody considered it a 
big deal. Yet today, it's a catastrophy... hmm.

Post a reply to this message

> ...not to mention traction control... ;-)

Er yeh, that's what I meant by wheel-spin.  OOC I looked up the instructions 
for how a dealer fits the "USB Audio" upgrade to my car (I was just 
wondering if the cables were already there and I simply needed to fit a 
suitable plug - sadly not).  Anyway, it appears my car has a network of 
fibre optic cables o_O.  To fit the upgrade, apparently involves ripping out 
half the car, making some connection to a box of opto-electronics in the 
boot, then fitting a "USB hub" under the drivers seat and fitting the USB 
socket in the centre console, and of course fitting cables between all of 
them.  The 250 pound price tag doesn't sound so bad now!

> The part I can't figure out is that, as far as I can tell, hooking up a 
> motor that turns the steering wheel in the same direction as you're trying 
> to turn it should generate a positive feedback loop. I can't figure out 
> how turning the wheel doesn't cause the powerful motors to rip the wheel 
> out of your hands and put the car into full lock before snapping the 
> steering column in half...

If you simply program the motor to apply the same torque you are applying 
with your hands to the wheel, then there is no feedback, it will just feel 
like it takes half the force to turn it.  Of course in reality it is more 
complex, the multiplier is probably dependant on speed, and maybe other 
factors like how sharp you are turning.  And maybe there is some limit the 
torque you apply needs to go above before the motor kicks in?

Something like:

If AppliedTorque > 10 Then
 MotorTorque = (AppliedTorque - 10) * CalculateAssistFactor( VehicleSpeed , 
SteerAngle )
Else
 MotorTorque = 0

Post a reply to this message

scott wrote:
>> ...not to mention traction control... ;-)
> 
> Er yeh, that's what I meant by wheel-spin.

ABS turns the brakes off if you brake too hard, traction control turns 
the drive off if you accelerate too hard. At least, as far as I know... ;-)

> OOC I looked up the 
> instructions for how a dealer fits the "USB Audio" upgrade to my car (I 
> was just wondering if the cables were already there and I simply needed 
> to fit a suitable plug - sadly not).  Anyway, it appears my car has a 
> network of fibre optic cables o_O.

Well... less suseptable to EMI and corrosion?

> To fit the upgrade, apparently 
> involves ripping out half the car, making some connection to a box of 
> opto-electronics in the boot, then fitting a "USB hub" under the drivers 
> seat and fitting the USB socket in the centre console, and of course 
> fitting cables between all of them.  The 250 pound price tag doesn't 
> sound so bad now!

LOL! Yeah. Apparently modern cars have quite big wiring looms inside 
them now. I remember one guy did some work on his own car, and then had 
to pay for an accredited shop to confirm that the airbag detonation 
system is still operating within spec.

Seriously though, you'd think they'd just put lots of spare cable in 
there so you can add new connections without rearranging half the car...

>> The part I can't figure out is that, as far as I can tell, hooking up 
>> a motor that turns the steering wheel in the same direction as you're 
>> trying to turn it should generate a positive feedback loop. I can't 
>> figure out how turning the wheel doesn't cause the powerful motors to 
>> rip the wheel out of your hands and put the car into full lock before 
>> snapping the steering column in half...
> 
> If you simply program the motor to apply the same torque you are 
> applying with your hands to the wheel, then there is no feedback, it 
> will just feel like it takes half the force to turn it.  Of course in 
> reality it is more complex, the multiplier is probably dependant on 
> speed, and maybe other factors like how sharp you are turning.  And 
> maybe there is some limit the torque you apply needs to go above before 
> the motor kicks in?

Oh, it's programmable? I thought it was a purely mechanical system...

Even so, how can you "sense" the amount of force the user it putting 
into the system seperately from the amount of force the power assist is 
putting into it? I can't think of a way of doing that.

Post a reply to this message

> ABS turns the brakes off if you brake too hard, traction control turns the 
> drive off if you accelerate too hard. At least, as far as I know... ;-)

Newer cars can apply the brakes too programmably, it's much faster than 
cutting the fuel and more accuracte, and when you are about to skid out 
sideways on a slippery road fast reactions are what you need.

> Well... less suseptable to EMI and corrosion?

Yeh the EMI issue is probably the biggest reason, especially now that they 
seem to be wanting to put more stuff in the back of the car to keep the 
weight distribution 50/50, it means you have long wires which are always bad 
from an EMI point of view.

> Seriously though, you'd think they'd just put lots of spare cable in there 
> so you can add new connections without rearranging half the car...

Guess it's cheaper not to, and then charge more for people who want to do 
stuff afterwards.

> Oh, it's programmable? I thought it was a purely mechanical system...

Older cars it was mechanical, yes, programmable (once!) by the positioning 
of the hydraulic valves :-)  Newer cars it's all electronic controlling a 
motor in software.

> Even so, how can you "sense" the amount of force the user it putting into 
> the system seperately from the amount of force the power assist is putting 
> into it? I can't think of a way of doing that.

Measure how much the steering column is twisted (ie rotation at one end 
minus rotation at the other end) between the steering wheel and where it 
connects to the rack/motor/hydraulics.  This will be directly proportional 
to the torque the driver is applying to the wheel, no matter what the motor 
or the wheels are doing.

In mechanical systems, this twist would cause hydraulic valves to open and 
assist the rack moving, in electronic systems there is probably just a 
strain gauge on the steering column that goes through an ATD to the 
software.

Post a reply to this message

scott wrote:

>> Well... less suseptable to EMI and corrosion?
> 
> Yeh the EMI issue is probably the biggest reason.

There would seem to be quite a lot of electronics in a car - especially 
a big alternator and a set of sparkplugs. That's gotta kick out a out of 
EMI, one would think...

>> Even so, how can you "sense" the amount of force the user it putting 
>> into the system seperately from the amount of force the power assist 
>> is putting into it? I can't think of a way of doing that.
> 
> Measure how much the steering column is twisted (ie rotation at one end 
> minus rotation at the other end) between the steering wheel and where it 
> connects to the rack/motor/hydraulics.  This will be directly 
> proportional to the torque the driver is applying to the wheel, no 
> matter what the motor or the wheels are doing.
> 
> In mechanical systems, this twist would cause hydraulic valves to open 
> and assist the rack moving, in electronic systems there is probably just 
> a strain gauge on the steering column that goes through an ATD to the 
> software.

I was under the impression that the rod is ridig, and therefore can't 
twist (only rotate).

Post a reply to this message

> I was under the impression that the rod is ridig, and therefore can't 
> twist (only rotate).

Nothing is perfectly rigid, a strain gauge on the rod will easily pick up 
the twist in a rod accurately enough to determine the torque and angle it is 
twisted.

On the older style mechanical systems they probably have a special small 
section that is a more flexible than the actual rod, that incorporates the 
valve design etc.

Post a reply to this message

scott wrote:
>> I was under the impression that the rod is ridig, and therefore can't 
>> twist (only rotate).
> 
> Nothing is perfectly rigid, a strain gauge on the rod will easily pick 
> up the twist in a rod accurately enough to determine the torque and 
> angle it is twisted.
> 
> On the older style mechanical systems they probably have a special small 
> section that is a more flexible than the actual rod, that incorporates 
> the valve design etc.

Mmm, OK.

Presumably you want it to not be *too* flexible though, lest the power 
steering mechanism stops working. It would be nice to still be able to 
steer. ;-)

Tell me, does this mean that there's no such thing as an inelastic 
collission outside of textbooks?

Post a reply to this message

Invisible <voi### [at] devnull> wrote:

> OOC, how much snow is there in the various other parts of the world
> where POVers are reading this??

Last Wednesday morning we had 12 inches.  When I looked outside, my Miata wasn't
much more than a bump in the driveway.  Since I live on a side road that usually
doesn't get plowed till late, I turned around and went back to bed.  Didn't make
it out until about 3PM.  All the roads are now clear, but we still have 8 to 10
inches of snow still on the ground.

Isaac

Post a reply to this message

Clarence1898 wrote:

> Last Wednesday morning we had 12 inches.  When I looked outside, my Miata wasn't
> much more than a bump in the driveway.  Since I live on a side road that usually
> doesn't get plowed till late, I turned around and went back to bed.  Didn't make
> it out until about 3PM.  All the roads are now clear, but we still have 8 to 10
> inches of snow still on the ground.

12 inches. Now that sounds like an actual snowfall.

OOC, where is this?

Post a reply to this message

> Presumably you want it to not be *too* flexible though, lest the power 
> steering mechanism stops working. It would be nice to still be able to 
> steer. ;-)

Well yes, I assume we're talking about "flexible" enough to allow a tiny jet 
of hydraulic fluid to open under really vigorous steering, not a bit of 
rubber that's going to twist through 180 degrees :-)

> 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.

Post a reply to this message

Invisible <voi### [at] devnull> wrote:
> Clarence1898 wrote:
>
> > Last Wednesday morning we had 12 inches.  When I looked outside, my Miata wasn't
> > much more than a bump in the driveway.  Since I live on a side road that usually
> > doesn't get plowed till late, I turned around and went back to bed.  Didn't make
> > it out until about 3PM.  All the roads are now clear, but we still have 8 to 10
> > inches of snow still on the ground.
>
> 12 inches. Now that sounds like an actual snowfall.
>
> OOC, where is this?

Indianapolis.  This was the worst snow in about 5 years.  Normally we'll get a 6
to 8 inch fall sometime during the winter.  So a little worse than usual but not
terrible.

Isaac

Post a reply to this message

>> OOC, where is this?
> 
> Indianapolis.  This was the worst snow in about 5 years.  Normally we'll get a 6
> to 8 inch fall sometime during the winter.  So a little worse than usual but not
> terrible.

Mmm, interesting. My company's HQ is in that state...

Post a reply to this message

Invisible <voi### [at] devnull> wrote:
> >> OOC, where is this?
> >
> > Indianapolis.  This was the worst snow in about 5 years.  Normally we'll get a 6
> > to 8 inch fall sometime during the winter.  So a little worse than usual but not
> > terrible.
>
> Mmm, interesting. My company's HQ is in that state...

Yes, very interesting.  The world can sometimes be a very small place.  AFAIK
the company I work for does not have any offices or subsidiaries in the UK.
Actually our corporate HQ is in NY,  IT and a distribution center is here in
Indiana.

Isaac.

Post a reply to this message

Invisible wrote:
> Seriously though, you'd think they'd just put lots of spare cable in 
> there so you can add new connections without rearranging half the car...

There are all kinds of shared-bus network protocols designed for inside of 
cars. You wouldn't be able to open your door for all the cables in the hings 
if all the devices in the door had their own wires.

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

Post a reply to this message

>>>> OOC, where is this?
>>> Indianapolis.
>> Mmm, interesting. My company's HQ is in that state...
> 
> Yes, very interesting.  The world can sometimes be a very small place.  AFAIK
> the company I work for does not have any offices or subsidiaries in the UK.
> Actually our corporate HQ is in NY,  IT and a distribution center is here in
> Indiana.

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! ;-)

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

Post a reply to this message

>> 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*

Post a reply to this message

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."

Post a reply to this message

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."

Post a reply to this message

> 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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Orchid XP v8 wrote:
> I would have through elastic would mean the objects deformed, and 
> inelastic would mean they didn't deform, but hey...

They both deform. The question is whether they spring back. If they didn't 
deform, they wouldn't bounce. Think about it, visualizing it at a tiny scale.

-- 
   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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On Mon, 02 Feb 2009 18:12:20 +0000, Orchid XP v8 wrote:

> 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?

Certainly not for you. :-)

> (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.)

That's interesting, because Salt Lake City is arranged on a grid as well.

> 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...

Yes, that would be a problem.  I wonder if it had done that last night?

Jim

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Invisible <voi### [at] devnull> wrote:
> For referense, *this* is "heavy snow":

> http://www.telenendaz.ch/documents/fond%20ecran/1024boardercross.jpg

  That's not heavy snow. This is heavy snow:

http://www.bbc.co.uk/wear/features/2004/12/images/weather_gallery/snow_in_canada_400x300.jpg

-- 
                                                          - Warp

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Warp wrote:
> Invisible <voi### [at] devnull> wrote:
>> For referense, *this* is "heavy snow":
> 
>> http://www.telenendaz.ch/documents/fond%20ecran/1024boardercross.jpg
> 
>   That's not heavy snow. This is heavy snow:
> 
>
http://www.bbc.co.uk/wear/features/2004/12/images/weather_gallery/snow_in_canada_400x300.jpg

Hah, that's a still from 'On Her Majesty's Secret Service', just before 
the line "He had lots of guts!"

;-)

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Darren New wrote:
> Orchid XP v8 wrote:
>> I would have through elastic would mean the objects deformed, and 
>> inelastic would mean they didn't deform, but hey...
> 
> They both deform. The question is whether they spring back. If they 
> didn't deform, they wouldn't bounce. Think about it, visualizing it at a 
> tiny scale.

Yes. I was saying, in a theoretical context, people often assume that 
objects collide with no deformation, but presumably in the real world 
this never actually happens...

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

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Warp wrote:
> Invisible <voi### [at] devnull> wrote:
>> For referense, *this* is "heavy snow":
> 
>> http://www.telenendaz.ch/documents/fond%20ecran/1024boardercross.jpg
> 
>   That's not heavy snow. This is heavy snow:
> 
>
http://www.bbc.co.uk/wear/features/2004/12/images/weather_gallery/snow_in_canada_400x300.jpg

...point conceeded. Warp wins!

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

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Invisible <voi### [at] devnull> wrote:
> I wonder if you could somehow plot this on a circular graph with a
> 12-month cycle?

Anything's possible, but conclusions are left as an exercise for the reader.
(divisions are 5 degrees Celsius.)

- Ricky

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