Re: A few silly questions


"Wayne Dobson" <nospam@xxxxxxxxxxxxx> wrote in message news:Qs2Bh.288$I46.229@xxxxxxxxxxxxxxxxxxxxxxxxxxxxx
"Androcles" <Engineer@xxxxxxxxxxxxxxxxxxxxxx> wrote in message
news:oNtAh.318085$MO2.56062@xxxxxxxxxxxxxxxxxxxxxxxxxxxx

Is there such a thing as instant acceleration?

Err... instantaneous velocity and instantaneous acceleration
are meaningful terms, the simplest example being the speedometer of a
car.
30 mph does not mean you have to travel 30 miles for a whole hour.
30 mph does not mean you have to travel 44 feet for a whole second.
30 mph does not mean you have to travel 0.44 feet for a whole 1/100th
second.

You can make the time interval as small as you like as long as it is not
zero.
Division-by-zero is undefined.

The problem I have with that conclusion is that 'instantaneous' implies a
zero division. Also, as I understand it, 'acceleration' is the measure
of
the rate of *change* of velocity and as nothing can change in zero time,
I
don't see how accerleration can be said to have taken place.

We know it does. Mathematics is a language used to describe physical
phenomena, but as with any language it has well-defined rules.
I cannot say "know We. does it" and expect you to recognise that as
a sensible statement, yet I've used exactly same words in a different
order.
Rules apply to mathematics also.

Absolutely! That's exactly the point I put across to David. I informed him
that I was aware that Physists have a particular way of speaking, which have
well defined meanings, but he could reasonably hold my words to the same
convention. He's acting like he can't glean the meaning of lay terms,
deliberately misconstruing my words, neglecting to ask for clarification,
then holding me to spurious conclusions, formed from this disingenuous
policy.

That is SOP (Standard Operating Procedure) for a moron when
defeated by reason. Instead of yielding they dig themselves a
deeper hole. Once you judge it deep enough, kick the dirt in on
top of them and bury them, they are useless anyway.


Instantaneous means as small as you like but not zero.

Right. That makes sense.

When I drive my car at a constant speed of 30 mph it is 30 mph
at exactly ANY point along the road. When I accelerate my car
it is traveling at exactly 30 mph at Point 1 and at 40 mph at Point 2,
so I accelerated between Point 1 and Point 2. Yet I cannot
*compute* or *calculate* my speed at exactly Point 1, I have
no distance between Point 1 and Point 1 and my speed is *calculated*
as distance divided by time. The computation would be 0/0, and that
is not allowed and meaningless. What I can do is calculate a small
distance, delta x and divide by a small time, delta t, or
dx/dt = 30 mph = 44 fps.

That was exactly my point. As far as I see it, without two distinct
reference points in time, with which to derive it, the notion of
acceleration is meaninless - not to speak of space.


There always have been two distinct points to an interval,
calculus is based on it.



The same rules applies to acceleration. I have speed 30 mph at P1
and 40 mph at P2, so there is a point between P1 and P2
where my speed must have been 35 mph, and four points where
my speed was 31,32,33,34 mph. Between those I have even finer
points where my speed is 31.1,31.2, 31.3 and so on and I can
go on getting smaller and smaller, never reaching zero, and *calculate*
my acceleration as finely as I wish, but I must never use zero.

Understood.

So... when I say instantaneous velocity at a point, it really is
30 mph at that point, but the computation is over an interval
that is not at the point but can be as small as I like.

I understand acceleration at a particular point, which pretty clear, but it
was put across like acceleration could take place in zero time.

Tempus fugit.


David is acting like one or more of three things is true:
He can't speak or understand plain English;
He can't conceptualise Physics;
He's dishonest.

As I said to you earlier, beware of muggles.
Muggles outnumber wizards and house elves 100: 1.

He who knows not and knows not that he knows not, he is a fool. Shun him.
He who knows not and knows that he knows not, he is a student. Teach him.
He who knows and knows not that he knows, he is a tool. Use him.
He who knows and knows that he knows, he is a sage. Follow him.


sci.physics has a lot of muggles, you'll soon see.
Look out for Blind Poe, he's a muggle.

Hahaha... You have a way with words.

Those wizards and elves of us that can do real magic have
learned our spells by experience, not just from incantations.

Ain't that the truth. I just left a bunch of parrots back at my old haunt,
to munch on bird seed.

They are mostly sheep in sci.physics and sci.physics.relativity.
I like to savage them.
http://www.androcles01.pwp.blueyonder.co.uk/SR.GIF


Do you like my broomstick?
It makes very short work of cobwebs and dust and it really flies.

This one does a good job,
http://www.defenselink.mil/specials/images/sightofsound.jpg

Mine was the Nimbus 1970 deluxe version:
http://tinyurl.com/57sza

Way cool toys! Hahaha...

That's REAL magic, but it's only magic if you don't know how it works.
It's not the paper magic tricks that theoretical physicists try to pull off.
They culminate in writing a "paper" that nobody will read anyway,
it always has a list of citations to back it up, never anything original.
They like to build castles in the air on the foundation of a house of cards.
Pull the rug out from under them and see them squeal and squirm,
it's great fun.

How far is it from A to A and how long does it take to get there?
http://www.androcles01.pwp.blueyonder.co.uk/DominoEffect.GIF

You wouldn't want to play Quidditch with it but it is
way faster than a hippogriff.

I think we have some hippogriffs in RMA: bird brains and horses asses.

RMA?
Even house elves can do some magic, that one has me beaten.

.

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