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On Wed, 13 Jan 2010 14:26:01 +0000, Invisible wrote:
> I still find it quite impressive that a CAR, which is made of METAL and
> powered by EXPLODING PETROL, can apparently be out-accelerated by a
> cheetah, which is MADE OF MEAT. Then again, an adult cheetah probably
> weighs significantly less than an Audi TT...
It's all about the power to weight ratio. :-)
Jim
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Darren New wrote:
> Actually, I was thinking of actual real space, where the same distances
> are different depending who is measuring them. What's a circle for me
> isn't a circle for you, so I find it hard to imagine a good definition
> for "pi" under such circumstances.
Do you mean as in special relativity? In such a case you'd probably
have to define a circle under the Minkowski metric, in which case it
won't look much like a circle. I *think* that in such a case all
circles end up having zero circumfrence, but I haven't actually worked
out the math so there's a good chance I'm wrong here.
Agreed that a pi-like constant really only makes sense in Euclidean
space though.
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Invisible wrote:
>
> So how *do* you compute the distance between two points in a non-Euclid
> space anyway?
Generally you start with a notion of something like a dot product
defined in the tangent spaces of your space and then write out an
integral to define the arc length of a curve. Then the distance between
two points can be defined to be the minimum length of any curve
connecting them.
> For that matter, is there a way to unambiguously refer to a specific
> point in such a space?
Depends on the space. A relatively general but computationally
cumbersome solution is to cover your space will small Cartesian patches
which connect together in a "nice" way. The you can define a point by
giving its Cartesian patch and its coordinates within that patch.
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Jim Henderson wrote:
> On Wed, 13 Jan 2010 14:26:01 +0000, Invisible wrote:
>
>> I still find it quite impressive that a CAR, which is made of METAL and
>> powered by EXPLODING PETROL, can apparently be out-accelerated by a
>> cheetah, which is MADE OF MEAT. Then again, an adult cheetah probably
>> weighs significantly less than an Audi TT...
>
> It's all about the power to weight ratio. :-)
Finally, somebody correctly identifies the issue... sheesh.
--
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*
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>> So how *do* you compute the distance between two points in a
>> non-Euclid space anyway?
>
> Generally you start with a notion of something like a dot product
> defined in the tangent spaces of your space and then write out an
> integral to define the arc length of a curve. Then the distance between
> two points can be defined to be the minimum length of any curve
> connecting them.
Any idea what the hell a tangent space is?
>> For that matter, is there a way to unambiguously refer to a specific
>> point in such a space?
>
> Depends on the space. A relatively general but computationally
> cumbersome solution is to cover your space will small Cartesian patches
> which connect together in a "nice" way. The you can define a point by
> giving its Cartesian patch and its coordinates within that patch.
Hmm, sounds like kind of a patchy solution...
--
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*
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On Wed, 13 Jan 2010 19:35:00 +0000, Orchid XP v8 wrote:
> Jim Henderson wrote:
>> On Wed, 13 Jan 2010 14:26:01 +0000, Invisible wrote:
>>
>>> I still find it quite impressive that a CAR, which is made of METAL
>>> and powered by EXPLODING PETROL, can apparently be out-accelerated by
>>> a cheetah, which is MADE OF MEAT. Then again, an adult cheetah
>>> probably weighs significantly less than an Audi TT...
>>
>> It's all about the power to weight ratio. :-)
>
> Finally, somebody correctly identifies the issue... sheesh.
Well, the others had good ideas as well - grip seems an important thing,
too - power on a ice vs. power on pavement end up with two vastly
different results.. :-)
Or was that sarcasm? ;-)
Jim
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>> Finally, somebody correctly identifies the issue... sheesh.
>
> Well, the others had good ideas as well - grip seems an important thing,
> too - power on a ice vs. power on pavement end up with two vastly
> different results.. :-)
>
> Or was that sarcasm? ;-)
Power is nothing without control, 'tis true. But most cars (and animals)
don't really have much of a problem with traction. The glaringly obvious
thing about fast animals (including the cheetah) is that they weigh
approximately nothing. Hell, fast cars tend to have the exact same
property! Except they're made of metal, which is strong, but quite heavy.
Of course, a cheetah can out-accelerate most cars, but has limited top
speed and severely limited endurance. But then again, if it doesn't kill
something in 90 seconds or so, the animal it's chasing won't give it
enough food to be worth continuing the chase anyway.
I gather the cheetah is limited primarily by overheating. Then again, it
leaves in a freakin' desert wilderness, after all...
--
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*
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Eero Ahonen wrote:
> Stephen wrote:
>> Eero Ahonen wrote:
>>
>>> - still having
>>> 150bhp/320Nm (upgradeable to 175bhp/370Nm with just a software) with
>> Let’s have an argument about the difference between hp and bhp, please. :-P
>>
>
> Bhp is a more defined unit than hp - bhp is the actual power that comes
> out of the engine (and goes to the gearbox).
>
> Well, actually bhp should be "braked" from the car itself - and they
> will be, after I'll upgrade the software.
>
> -Aero
Do you call that an argument? LOL
From my memory of mechanics at school, hp was more an advertising unit ;)
Bloody farmers couldn’t tell an erg from an egg :-)
--
Best Regards,
Stephen
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scott wrote:
> Didn't the UK car tax depend on the displacement of your engine?
I don't know about the UK, but the USA both taxes and bases some
insurance off of displacement.
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On Wed, 13 Jan 2010 20:33:02 +0000, Orchid XP v8 wrote:
> Power is nothing without control, 'tis true. But most cars (and animals)
> don't really have much of a problem with traction. The glaringly obvious
> thing about fast animals (including the cheetah) is that they weigh
> approximately nothing. Hell, fast cars tend to have the exact same
> property! Except they're made of metal, which is strong, but quite
> heavy.
True - though many newer cars are lighter than older counterparts, what
with using machined aluminium, carbon fibre, and other such composites
(many of which come from the aerospace industry where high strength and
low weight are absolutely necessary features), there's no doubt they
still weigh more than the average cheetah. :-)
> Of course, a cheetah can out-accelerate most cars, but has limited top
> speed and severely limited endurance. But then again, if it doesn't kill
> something in 90 seconds or so, the animal it's chasing won't give it
> enough food to be worth continuing the chase anyway.
Yep, and often they'll abandon the chase when it becomes apparent that
nothing useful comes from it.
> I gather the cheetah is limited primarily by overheating. Then again, it
> leaves in a freakin' desert wilderness, after all...
True. :-)
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