Another Larry Brasfield Self-Aggrandizing Put-Down Anecdote

Fred Bloggs · Mar 22, 2005

Look at the total schizoid fake make more stuff up- a real zero- this is
getting so old:

From: "Larry Brasfield" <donotspam_larry_brasfi...@hotmail.com>
Newsgroups: sci.electronics.basics
References: <bd24a397.0503080128.77ba467e@posting.google.com>
<uMGdnQ0E54dKlbPfRVn-tw@comcast.com>
Subject: Re: Potentially painful
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"Robert Monsen" <rcsurn...@comcast.net> wrote in message
news:uMGdnQ0E54dKlbPfRVn-tw@comcast.com...

No, as I recall, kinetic energy is 1/2 * m * v^2.

I recall seeing that claim from a high school physics teacher when
I was a smart-ass twerp. I posed the following puzzle to him:
A rocket car starts at rest, accellerating at a constant rate
because its thrust is constant. It is burning fuel at a constant
rate to produce that constant thrust. The kinetic energy of
the rocket car is allegedly M * V^2 / 2, so it is increasing
quadratically versus time. But the fuel consumed increases
only linearly with time. How can this be?

I would be interested in your take on this. My physics teacher
could not resolve it, (but, to his credit, that bothered him).

--
--Larry Brasfield
email: donotspam_larry_brasfi...@hotmail.com
Above views may belong only to me.

Active8 · Mar 22, 2005

On Tue, 22 Mar 2005 11:45:04 GMT, Fred Bloggs wrote:

Look at the total schizoid fake make more stuff up- a real zero- this is
getting so old:

From: "Larry Brasfield" <donotspam_larry_brasfi...@hotmail.com
Newsgroups: sci.electronics.basics
References: <bd24a397.0503080128.77ba467e@posting.google.com
uMGdnQ0E54dKlbPfRVn-tw@comcast.com
Subject: Re: Potentially painful
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Date: Tue, 8 Mar 2005 12:44:56 -0800
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14:44:57 CST)
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"Robert Monsen" <rcsurn...@comcast.net> wrote in message
news:uMGdnQ0E54dKlbPfRVn-tw@comcast.com...
No, as I recall, kinetic energy is 1/2 * m * v^2.

I recall seeing that claim from a high school physics teacher when
I was a smart-ass twerp. I posed the following puzzle to him:
A rocket car starts at rest, accellerating at a constant rate
because its thrust is constant. It is burning fuel at a constant
rate to produce that constant thrust. The kinetic energy of
the rocket car is allegedly M * V^2 / 2, so it is increasing
quadratically versus time. But the fuel consumed increases
only linearly with time. How can this be?

I would be interested in your take on this. My physics teacher
could not resolve it, (but, to his credit, that bothered him).

The instantaneous kinetic E obeys .5*m*v^2, but the total solution
would require a partial diff eq.
--
Best Regards,
Mike

Jim Thompson · Mar 22, 2005

On Tue, 22 Mar 2005 19:12:04 -0500, Active8 <reply2group@ndbbm.net>
wrote:

On Tue, 22 Mar 2005 18:50:15 -0500, Active8 wrote:

On Tue, 22 Mar 2005 18:06:05 -0500, Active8 wrote:

On Tue, 22 Mar 2005 11:45:04 GMT, Fred Bloggs wrote:

Look at the total schizoid fake make more stuff up- a real zero- this is
getting so old:

From: "Larry Brasfield" <donotspam_larry_brasfi...@hotmail.com
snip

"Robert Monsen" <rcsurn...@comcast.net> wrote in message
news:uMGdnQ0E54dKlbPfRVn-tw@comcast.com...
No, as I recall, kinetic energy is 1/2 * m * v^2.

I recall seeing that claim from a high school physics teacher when
I was a smart-ass twerp. I posed the following puzzle to him:
A rocket car starts at rest, accellerating at a constant rate
because its thrust is constant. It is burning fuel at a constant
rate to produce that constant thrust. The kinetic energy of
the rocket car is allegedly M * V^2 / 2, so it is increasing
quadratically versus time. But the fuel consumed increases
only linearly with time. How can this be?

And WTF? The equation for E is not a claim, it's a fact. The last 3
sentences above are so indicative of flawed logic ( or trolling )
that they defy comment.

If I shit a pound per day and grow shit^2 pounds of tomatoes a year
for shit^3 kcal of energy... I'm shitting linearly, growing
quadratically, and consuming cubically. I shit you not, larry.
You're my favorite turd this week.

Congratulations for most colorful language of the week

But beware the Brasfield, there's mendacity hidden in his problem
description. Try solving this versus time, not just end point.

I would be interested in your take on this. My physics teacher
could not resolve it, (but, to his credit, that bothered him).

The instantaneous kinetic E obeys .5*m*v^2, but the total solution
would require a partial diff eq.

Better yet, if you know the mass *and* speed of the ejected fuel,
conservation of momentum is the easiest solution.

M_r = mass of rocket and fuel, pre-burn
V_r = velocity of rocket and fuel, pre-burn
m_r = mass of rocket, post burn.
v_r = velocity of rocket, post burn
v_f = velocity of ejected fuel, post burn
m_f = mass of ejected fuel, post burn

M_r * V_r = m_r * v_r + m_f * v_f

A stumped physics teacher does not a smart larry make.

480)460-2350 | |
| E-mail Address at Website Fax

Larry Brasfield · Mar 22, 2005

"Active8" <reply2group@ndbbm.net> wrote in message
news:1undbh2xrxhm0$.dlg@ID-222894.news.individual.net...
Brasfield once wrote:

I recall seeing that claim from a high school physics teacher when
I was a smart-ass twerp. I posed the following puzzle to him:
A rocket car starts at rest, accellerating at a constant rate
because its thrust is constant. It is burning fuel at a constant
rate to produce that constant thrust. The kinetic energy of
the rocket car is allegedly M * V^2 / 2, so it is increasing
quadratically versus time. But the fuel consumed increases
only linearly with time. How can this be?

And WTF? The equation for E is not a claim, it's a fact. The last 3
sentences above are so indicative of flawed logic ( or trolling )
that they defy comment.

Well, your "fact" is not accepted physics today. It is a very
good approximation for velocities well below the speed of
light, but it cannot be defended as gold plated Truth.
If you doubt this, look here:
http://www.kineticbooks.com/physics/17467/17516/sp.html
or search on words: "kinetic energy" formula relativistic .

That said, I will admit to phrasing my doubt of the matter
in a provocative way. If that makes me a troll, so be it.
But I posted it because I thought it was an interesting
puzzler. The physics are fairly simple, (as you have
suggested), but only if you consider the right set of
objects. The puzzle is one that took me in as a high
school student, along with a smart friend and my high
school physics teacher who was dedicated and good
at what he did. So, I thought it had a good chance of
puzzling folks who were following the thread up to then.
All in good fun, and not a typical troll.

You're my favorite turd this week.

I'm glad to not be acquainted with the others, then.

Better yet, if you know the mass *and* speed of the ejected fuel,
conservation of momentum is the easiest solution.

M_r = mass of rocket and fuel, pre-burn
V_r = velocity of rocket and fuel, pre-burn
m_r = mass of rocket, post burn.
v_r = velocity of rocket, post burn
v_f = velocity of ejected fuel, post burn
m_f = mass of ejected fuel, post burn

M_r * V_r = m_r * v_r + m_f * v_f

A stumped physics teacher does not a smart larry make.

Agreed, certainly.

I take his having been stumped only as an indicator that
the problem induces a mindset that can make it hard.
As you have shown, and as I puzzled out a few years
later, and as several other people showed here, it is not
that challenging once you get out of that mindset.

There is another point lurking here, worth addressing
since you bring it up and a few take it as an article of
faith. Showing another person to be smart or not has
no bearing on how smart the shower may be.

What my noisy vile shadow has missed, (and you too,
it seems), is that I was as puzzled as my teacher. How
that scene, of a teacher and student both wondering how
to resolve a paradox, can possibly show the student to
be putting down the teacher, or to be smarter, is quite
mystefying to me. I think that vile interpretation has to
be yet another instance of the projection I manage to
induce among a (very) few folks here.

--
--Larry Brasfield
email: donotspam_larry_brasfield@hotmail.com
Above views may belong only to me.

Active8 · Mar 23, 2005

On Tue, 22 Mar 2005 17:28:55 -0700, Jim Thompson wrote:

<snip>

But beware the Brasfield, there's mendacity hidden in his problem
description. Try solving this versus time, not just end point.

Mendacity... good word, but it's flawed logic at best. See my reply
to the beginning of the broken thread that not surprizingly, was
detected by my script as a reply 'cause the headers and x-refs
retained integrity.

My guess would be to set up a partial diff eq. of f( m(t),v(t) )

Oh, I see another flaw I must include.

--
Best Regards,
Mike

Jim Thompson · Mar 23, 2005

On Tue, 22 Mar 2005 20:38:58 -0500, Active8 <reply2group@ndbbm.net>
wrote:

On Tue, 22 Mar 2005 17:28:55 -0700, Jim Thompson wrote:

snip

But beware the Brasfield, there's mendacity hidden in his problem
description. Try solving this versus time, not just end point.

Mendacity... good word, but it's flawed logic at best. See my reply
to the beginning of the broken thread that not surprizingly, was
detected by my script as a reply 'cause the headers and x-refs
retained integrity.

My guess would be to set up a partial diff eq. of f( m(t),v(t) )

Oh, I see another flaw I must include.

I've developed a feeling that Brasfield is always trying to set one
up, just like that "ldg" turkey with his wanderings about Spice
analysis.

Nothing he uttered ever made sense... like he can't read, yet he
concluded, "I was curious at that point what you might actually know.
Not curious now."

I hope that made him feel good, because he can't even find his own
fookin' arse with both hands and a mirror ;-)

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice

480)460-2350 | |
| E-mail Address at Website Fax

Active8 · Mar 23, 2005

On Tue, 22 Mar 2005 16:53:22 -0800, Larry Brasfield wrote:

"Active8" <reply2group@ndbbm.net> wrote in message
news:1undbh2xrxhm0$.dlg@ID-222894.news.individual.net...
Brasfield once wrote:
I recall seeing that claim from a high school physics teacher when
I was a smart-ass twerp. I posed the following puzzle to him:
A rocket car starts at rest, accellerating at a constant rate
because its thrust is constant. It is burning fuel at a constant
rate to produce that constant thrust. The kinetic energy of
the rocket car is allegedly M * V^2 / 2, so it is increasing
quadratically versus time. But the fuel consumed increases
only linearly with time. How can this be?

And WTF? The equation for E is not a claim, it's a fact. The last 3
sentences above are so indicative of flawed logic ( or trolling )
that they defy comment.

Well, your "fact" is not accepted physics today. It is a very
good approximation for velocities well below the speed of
light, but it cannot be defended as gold plated Truth.
If you doubt this, look here:
http://www.kineticbooks.com/physics/17467/17516/sp.html
or search on words: "kinetic energy" formula relativistic .

Rockets travel well below the speed of light, last I checked. So the
above is irrelevant to the discussion.

That said, I will admit to phrasing my doubt of the matter
in a provocative way. If that makes me a troll, so be it.
But I posted it because I thought it was an interesting
puzzler.

It is, but it looks more like you were trying to make your physics
teacher look dumb and you smart by posing a question you couldn't
answer. Hey. I stumped the algebra teacher across the street by
mentioning "too many variables" in a given prob. She gave up and
agreed. If I'd have kept my mouth shut, she might have looked at the
prob differently. I posted to the "Twist You Noodle" forum and
someone pulled my head out of my ass for me.

The physics are fairly simple, (as you have
suggested), but only if you consider the right set of
objects. The puzzle is one that took me in as a high
school student, along with a smart friend and my high
school physics teacher who was dedicated and good
at what he did. So, I thought it had a good chance of
puzzling folks who were following the thread up to then.
All in good fun, and not a typical troll.

I'm not a bit puzzled. The flawed logic is the assumption that a
linear decrease in fuel mass is contrary to a quadratic increase in
kinetic energy. And that *instantaneous E" or better yet

|
E = .5 * m * V^2 |
|m=k

variable mass is another story.

And to hint that it breaks E = .5*m*v^2 is incorrect.

And now I see the mandacity that Jim alluded to. E does not vary
quadratically with time, it varies quadratically with velocity

snip

A stumped physics teacher does not a smart larry make.

Agreed, certainly.

<snip>

What my noisy vile shadow has missed, (and you too,
it seems), is that I was as puzzled as my teacher. How
that scene, of a teacher and student both wondering how
to resolve a paradox, can possibly show the student to
be putting down the teacher, or to be smarter, is quite
mystefying to me. I think that vile interpretation has to
be yet another instance of the projection I manage to
induce among a (very) few folks here.

I didn't miss that. I've seen a few threadss over the past days that
indicate that you're trying to prove you're smart. If nothing, I've
learned a bit about how not to post. I'll try.

I have to get showered for a date. Maybe I'll look at the seb thread
while I dry. You can turn the clock off, because I won't be
researching this subject. I'll let you know when I have to run to
the books.
--
Best Regards,
Mike

Active8 · Mar 23, 2005

On Tue, 22 Mar 2005 20:45:21 -0500, Active8 wrote:

<snip>

And now I see the mandacity that Jim alluded to. E does not vary
quadratically with time, it varies quadratically with velocity

[drip, drip, drip, ...]

Eh, t^2 does still show up, so maybe the other gotcha is in the
assumption of a quadratic vs linear relationship. I'll try it on my
napkin when she goes to powder her ... whatever.
<snip>
--
Best Regards,
Mike

Jim Thompson · Mar 23, 2005

On Tue, 22 Mar 2005 20:57:44 -0500, Active8 <reply2group@ndbbm.net>
wrote:

On Tue, 22 Mar 2005 20:45:21 -0500, Active8 wrote:

snip

And now I see the mandacity that Jim alluded to. E does not vary
quadratically with time, it varies quadratically with velocity

[drip, drip, drip, ...]

Eh, t^2 does still show up, so maybe the other gotcha is in the
assumption of a quadratic vs linear relationship. I'll try it on my
napkin when she goes to powder her ... whatever.
snip

480)460-2350 | |
| E-mail Address at Website Fax

Fred Bloggs · Mar 23, 2005

Active8 wrote:

On Tue, 22 Mar 2005 16:53:22 -0800, Larry Brasfield wrote:

"Active8" <reply2group@ndbbm.net> wrote in message
news:1undbh2xrxhm0$.dlg@ID-222894.news.individual.net...
Brasfield once wrote:

I recall seeing that claim from a high school physics teacher when
I was a smart-ass twerp. I posed the following puzzle to him:
A rocket car starts at rest, accellerating at a constant rate
because its thrust is constant. It is burning fuel at a constant
rate to produce that constant thrust. The kinetic energy of
the rocket car is allegedly M * V^2 / 2, so it is increasing
quadratically versus time. But the fuel consumed increases
only linearly with time. How can this be?

And WTF? The equation for E is not a claim, it's a fact. The last 3
sentences above are so indicative of flawed logic ( or trolling )
that they defy comment.

Well, your "fact" is not accepted physics today. It is a very
good approximation for velocities well below the speed of
light, but it cannot be defended as gold plated Truth.
If you doubt this, look here:
http://www.kineticbooks.com/physics/17467/17516/sp.html
or search on words: "kinetic energy" formula relativistic .

Rockets travel well below the speed of light, last I checked. So the
above is irrelevant to the discussion.

That said, I will admit to phrasing my doubt of the matter
in a provocative way. If that makes me a troll, so be it.
But I posted it because I thought it was an interesting
puzzler.

It is, but it looks more like you were trying to make your physics
teacher look dumb and you smart by posing a question you couldn't
answer. Hey. I stumped the algebra teacher across the street by
mentioning "too many variables" in a given prob. She gave up and
agreed. If I'd have kept my mouth shut, she might have looked at the
prob differently. I posted to the "Twist You Noodle" forum and
someone pulled my head out of my ass for me.

The physics are fairly simple, (as you have
suggested), but only if you consider the right set of
objects. The puzzle is one that took me in as a high
school student, along with a smart friend and my high
school physics teacher who was dedicated and good
at what he did. So, I thought it had a good chance of
puzzling folks who were following the thread up to then.
All in good fun, and not a typical troll.

I'm not a bit puzzled. The flawed logic is the assumption that a
linear decrease in fuel mass is contrary to a quadratic increase in
kinetic energy. And that *instantaneous E" or better yet

|
E = .5 * m * V^2 |
|m=k

variable mass is another story.

And to hint that it breaks E = .5*m*v^2 is incorrect.

And now I see the mandacity that Jim alluded to. E does not vary
quadratically with time, it varies quadratically with velocity

snip

A stumped physics teacher does not a smart larry make.

Agreed, certainly.

snip

What my noisy vile shadow has missed, (and you too,
it seems), is that I was as puzzled as my teacher. How
that scene, of a teacher and student both wondering how
to resolve a paradox, can possibly show the student to
be putting down the teacher, or to be smarter, is quite
mystefying to me. I think that vile interpretation has to
be yet another instance of the projection I manage to
induce among a (very) few folks here.

I didn't miss that. I've seen a few threadss over the past days that
indicate that you're trying to prove you're smart. If nothing, I've
learned a bit about how not to post. I'll try.

I have to get showered for a date. Maybe I'll look at the seb thread
while I dry. You can turn the clock off, because I won't be
researching this subject. I'll let you know when I have to run to
the books.

This Brasfield has to be the most ostentatious pseudo-intellectual on
USENET- and gets his ass handed to him all the time. The mental midget
jumps from one parameter to another , related by some means unknown to
him, and suggests it constitutes a conundrum. This is such puerile
garbage- and only a pseudo-intellectual could consider it an event. And
do you notice how pseudo-intellectuals just love arguing fundamentals,
definitions, and semantics. Brasfield is true USENET garbage.

Ratch · Mar 23, 2005

"Fred Bloggs" <nospam@nospam.com> wrote in message
news:4240053D.1040603@nospam.com...

No, as I recall, kinetic energy is 1/2 * m * v^2.

I recall seeing that claim from a high school physics teacher when
I was a smart-ass twerp. I posed the following puzzle to him:
A rocket car starts at rest, accellerating at a constant rate
because its thrust is constant. It is burning fuel at a constant
rate to produce that constant thrust. The kinetic energy of
the rocket car is allegedly M * V^2 / 2, so it is increasing
quadratically versus time. But the fuel consumed increases
only linearly with time. How can this be?

I would be interested in your take on this. My physics teacher
could not resolve it, (but, to his credit, that bothered him).

Let's assume that the amount of fuel burned at the end of the run is
insignificant when compared with the total weight of the rocket. Then we
don't have to worry about mass differentials during the run. Let's further
assume that all the fuel is converted into thrust with no heat, so we don't
have to worry about energy diversions.

First I will explain why the rocket is NOT burning fuel at a constant rate
to produce constant thrust. And if that is true, it follows that fuel
consumed does not increase linearly with time.

Let's assume at takeoff, acceleration is 2 meter/sec˛ and an initial
velocity of zero. Within 1 second and a distance of 1 meter, enough fuel
has to be burned to increase the velocity to 2 meter/sec. Now it clears the
gantry at a velocity of 10 meters/sec. If the velocity stayed constant, it
would go 1 meter in a 1/10 of a sec. But we assume constant acceleration,
so it has less than 1/10 of a sec to increase its velocity. It clears the
clouds at a velocity of 100 meter/sec. Now it has less than 1/100 of a sec
to increase its velocity within 1 meter. As you can see, due to its higher
speed, the rocket has less time to increase its velocity with 1 meter, which
because of its constant acceleration it must do. So what happens? It has
to burn up its fuel faster and faster to create more thrust, so it can beat
the deadline of a higher velocity with the 1 meter measuring reference.
That is why it takes 3 times the energy to increase a velocity from 50 to
100 distance units/sec as it does from 0 to 50 distance units/sec. Ratch

Active8 · Mar 23, 2005

On Tue, 22 Mar 2005 21:31:15 -0800, Larry Brasfield wrote:

"Active8" <reply2group@ndbbm.net> wrote in message
newsxi1f69au1tb$.dlg@ID-222894.news.individual.net...
On Tue, 22 Mar 2005 16:53:22 -0800, Larry Brasfield wrote:
snip
You assume facts not in evidence. What leads you to
believe this happened in front of a classroom of kids?

This NG is a type of classroom. Regardles of who was present then,
it looked like you wanted to prove something to us. Forget it.
You'll have plenty of opportunities to reveal yourself one way or
the other.

As a matter of fact, it occured after school during one
of many half-hour sessions he and I spent. How could
a teenager expect that his teacher would not be able to
answer such a question? What evidence supports the
allegation that it was anything but a curious kid asking
an expert a question that puzzled him?

How about the admission that you were being your typical smart-assed
self?

I posted to the "Twist You Noodle" forum and
someone pulled my head out of my ass for me.

Looking for more of your favorites, were you?

The physics are fairly simple, (as you have
suggested), but only if you consider the right set of
objects. The puzzle is one that took me in as a high
school student, along with a smart friend and my high
school physics teacher who was dedicated and good
at what he did. So, I thought it had a good chance of
puzzling folks who were following the thread up to then.
All in good fun, and not a typical troll.

I'm not a bit puzzled. The flawed logic is the assumption that a
linear decrease in fuel mass is contrary to a quadratic increase in
kinetic energy.

Yes, that is the key. There is an implicit (but incorrect)
reliance on the notion of energy conservation, while
paying attention to only 2 of the 3 players. The burnt
fuel and the rocket are visible, the exhaust is invisible.

The exhaust *is* the burnt fuel. Same fuel mass (if oxidized from an
onboard source), different place and chemical composition.

(If you ever do this on a whiteboard for someone else's
puzzlement, be sure to not draw an exhaust plume!)

And that *instantaneous E" or better yet

|
E = .5 * m * V^2 |
|m=k

variable mass is another story.

And way beyond anybody's attention if actually dealt with.

And to hint that it breaks E = .5*m*v^2 is incorrect.

It could hardly be a puzzle without that dilemma.

When I get to it on paper, I doubt there will be a dilemma.

And now I see the mandacity that Jim alluded to. E does not vary
quadratically with time, it varies quadratically with velocity

Under the stated assumptions of the problem, "accellerating at a
constant rate", the velocity varies linearly with time. Therefore
the kinetic energy varies quadratically with time and velocity.
I fail to see how mendacity enters into this.

If Jim really meant to say "mendacity", I'll find something.
Otherwise, he meant "trick question, and I'll still find something.
My reply to myself indicates that I realized the error of my
statement while I was in the shower. I like noodle twisters.
--
Best Regards,
Mike

Active8 · Mar 23, 2005

On Tue, 22 Mar 2005 19:08:32 -0700, Jim Thompson wrote:

On Tue, 22 Mar 2005 20:57:44 -0500, Active8 <reply2group@ndbbm.net
wrote:

On Tue, 22 Mar 2005 20:45:21 -0500, Active8 wrote:

snip

And now I see the mandacity that Jim alluded to. E does not vary
quadratically with time, it varies quadratically with velocity

[drip, drip, drip, ...]

Eh, t^2 does still show up, so maybe the other gotcha is in the
assumption of a quadratic vs linear relationship. I'll try it on my
napkin when she goes to powder her ... whatever.
snip

Don't do that. As Confucius say, "It is better to get laid than to
solve Algebra problem and appear smart-ass to date." ;-)

My usual funny dickhead approach served me well enough for a first
date. We hit it off well. I thought she'd be a bore or closed
minded, but she's more of a free thinker than I expected.

I slipped the napkin thing in undetected, but by the time I got the
waitress's pen, I only had time to write what I'd already done in my
head. For my next act, I'll teach her to empty ashtrays and clear
off the empty sugar pouches as if grabbing clean ash trays from the
next table weren't hint enough

I think she learned not to spill
coffee on me, though

--
Best Regards,
Mike

Larry Brasfield · Mar 23, 2005

"John - KD5YI" <kd5yikes@mindspring.com> wrote in message
news:T5g0e.1972$gI5.1121@newsread1.news.pas.earthlink.net...

Fred Bloggs wrote:
[Irrelevant FB spew cut. Irrelevant and scurrilous FB subject revised.]
"Robert Monsen" <rcsurn...@comcast.net> wrote in message
news:uMGdnQ0E54dKlbPfRVn-tw@comcast.com...
No, as I recall, kinetic energy is 1/2 * m * v^2.

I recall seeing that claim from a high school physics teacher when
I was a smart-ass twerp. I posed the following puzzle to him:
A rocket car starts at rest, accellerating at a constant rate
because its thrust is constant. It is burning fuel at a constant
rate to produce that constant thrust. The kinetic energy of
the rocket car is allegedly M * V^2 / 2, so it is increasing
quadratically versus time. But the fuel consumed increases
only linearly with time. How can this be?

I would be interested in your take on this. My physics teacher
could not resolve it, (but, to his credit, that bothered him).

I do not understand how acceleration can be constant due to constant thrust when the mass is changing (fuel depletion). This seems
to me to be a contradiction.

Think of it as an engineering approximation.
For an atomic powered, ion rocket engine,
it can be a very close approximation.

The reason to make the approximation is
to keep the math simple. The error is not
relevant to the puzzle's apparent dilemma,
so the extra math would be a distraction.

--
--Larry Brasfield
email: donotspam_larry_brasfield@hotmail.com
Above views may belong only to me.

Active8 · Mar 23, 2005

On Wed, 23 Mar 2005 01:53:44 -0600, Ratch wrote:

"Fred Bloggs" <nospam@nospam.com> wrote in message
news:4240053D.1040603@nospam.com...
No, as I recall, kinetic energy is 1/2 * m * v^2.

I recall seeing that claim from a high school physics teacher when
I was a smart-ass twerp. I posed the following puzzle to him:
A rocket car starts at rest, accellerating at a constant rate
because its thrust is constant. It is burning fuel at a constant
rate to produce that constant thrust. The kinetic energy of
the rocket car is allegedly M * V^2 / 2, so it is increasing
quadratically versus time. But the fuel consumed increases
only linearly with time. How can this be?

I would be interested in your take on this. My physics teacher
could not resolve it, (but, to his credit, that bothered him).

Let's assume that the amount of fuel burned at the end of the run is
insignificant when compared with the total weight of the rocket. Then we
don't have to worry about mass differentials during the run. Let's further
assume that all the fuel is converted into thrust with no heat, so we don't
have to worry about energy diversions.

First I will explain why the rocket is NOT burning fuel at a constant rate
to produce constant thrust. And if that is true, it follows that fuel
consumed does not increase linearly with time.

Let's assume at takeoff, acceleration is 2 meter/sec˛ and an initial
velocity of zero. Within 1 second and a distance of 1 meter, enough fuel
has to be burned to increase the velocity to 2 meter/sec. Now it clears the
gantry at a velocity of 10 meters/sec. If the velocity stayed constant, it
would go 1 meter in a 1/10 of a sec. But we assume constant acceleration,
so it has less than 1/10 of a sec to increase its velocity. It clears the
clouds at a velocity of 100 meter/sec. Now it has less than 1/100 of a sec
to increase its velocity within 1 meter. As you can see, due to its higher
speed, the rocket has less time to increase its velocity with 1 meter, which
because of its constant acceleration it must do. So what happens? It has
to burn up its fuel faster and faster to create more thrust, so it can beat
the deadline of a higher velocity with the 1 meter measuring reference.
That is why it takes 3 times the energy to increase a velocity from 50 to
100 distance units/sec as it does from 0 to 50 distance units/sec. Ratch

But increased thrust (force) implies increased acceleration.
--
Best Regards,
Mike

John - KD5YI · Mar 24, 2005

Active8 wrote:

On Wed, 23 Mar 2005 15:40:35 GMT, John - KD5YI wrote:

Fred Bloggs wrote:

Look at the total schizoid fake make more stuff up- a real zero- this is
getting so old:

From: "Larry Brasfield" <donotspam_larry_brasfi...@hotmail.com
Newsgroups: sci.electronics.basics
References: <bd24a397.0503080128.77ba467e@posting.google.com
uMGdnQ0E54dKlbPfRVn-tw@comcast.com
Subject: Re: Potentially painful
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"Robert Monsen" <rcsurn...@comcast.net> wrote in message
news:uMGdnQ0E54dKlbPfRVn-tw@comcast.com...
No, as I recall, kinetic energy is 1/2 * m * v^2.

I recall seeing that claim from a high school physics teacher when
I was a smart-ass twerp. I posed the following puzzle to him:
A rocket car starts at rest, accellerating at a constant rate
because its thrust is constant. It is burning fuel at a constant
rate to produce that constant thrust. The kinetic energy of
the rocket car is allegedly M * V^2 / 2, so it is increasing
quadratically versus time. But the fuel consumed increases
only linearly with time. How can this be?

I would be interested in your take on this. My physics teacher
could not resolve it, (but, to his credit, that bothered him).

I do not understand how acceleration can be constant due to constant thrust
when the mass is changing (fuel depletion). This seems to me to be a
contradiction.

That's a good candidate for the "mendacity hidden in his problem
description." that JT warned me about.

Well, since it was not part of the original post, it feels like changing the
rules to me.

Rich Grise · Mar 24, 2005

On Thu, 24 Mar 2005 02:31:40 +0000, John - KD5YI wrote:

Active8 wrote:
On Wed, 23 Mar 2005 15:40:35 GMT, John - KD5YI wrote:
Fred Bloggs wrote:
From: "Larry Brasfield" <donotspam_larry_brasfi...@hotmail.com
"Robert Monsen" <rcsurn...@comcast.net> wrote in message
No, as I recall, kinetic energy is 1/2 * m * v^2.
I recall seeing that claim from a high school physics teacher when
I was a smart-ass twerp. I posed the following puzzle to him:
A rocket car starts at rest, accellerating at a constant rate
because its thrust is constant. It is burning fuel at a constant
rate to produce that constant thrust. The kinetic energy of
the rocket car is allegedly M * V^2 / 2, so it is increasing
quadratically versus time. But the fuel consumed increases
only linearly with time. How can this be?

I would be interested in your take on this. My physics teacher
could not resolve it, (but, to his credit, that bothered him).

I do not understand how acceleration can be constant due to constant thrust
when the mass is changing (fuel depletion). This seems to me to be a
contradiction.

That's a good candidate for the "mendacity hidden in his problem
description." that JT warned me about.

Well, since it was not part of the original post, it feels like changing the
rules to me.

It's not "changing the rules". It's pointing out that the assertion, "A
rocket car starts at rest, accellerating at a constant rate because its
thrust is constant. It is burning fuel at a constant rate to produce that
constant thrust." is impossible, so the question is meaningless.

If the rocket car is experiencing constant thrust, it will accellerate
at a constant rate IF ITS MASS IS NOT CHANGING.

If it is burning fuel at a constant rate, and the thrust is constant,
then the accelleration would increase because the mass is decreasing.

I thought this got done with weeks ago.

Thanks,
Rich

Active8 · Mar 24, 2005

On Thu, 24 Mar 2005 04:13:58 GMT, Rich Grise wrote:

On Thu, 24 Mar 2005 02:31:40 +0000, John - KD5YI wrote:
Active8 wrote:
On Wed, 23 Mar 2005 15:40:35 GMT, John - KD5YI wrote:
Fred Bloggs wrote:
From: "Larry Brasfield" <donotspam_larry_brasfi...@hotmail.com
"Robert Monsen" <rcsurn...@comcast.net> wrote in message
No, as I recall, kinetic energy is 1/2 * m * v^2.
I recall seeing that claim from a high school physics teacher when
I was a smart-ass twerp. I posed the following puzzle to him:
A rocket car starts at rest, accellerating at a constant rate
because its thrust is constant. It is burning fuel at a constant
rate to produce that constant thrust. The kinetic energy of
the rocket car is allegedly M * V^2 / 2, so it is increasing
quadratically versus time. But the fuel consumed increases
only linearly with time. How can this be?

I would be interested in your take on this. My physics teacher
could not resolve it, (but, to his credit, that bothered him).

I do not understand how acceleration can be constant due to constant thrust
when the mass is changing (fuel depletion). This seems to me to be a
contradiction.

That's a good candidate for the "mendacity hidden in his problem
description." that JT warned me about.

Well, since it was not part of the original post, it feels like changing the
rules to me.

It's not "changing the rules". It's pointing out that the assertion, "A
rocket car starts at rest, accellerating at a constant rate because its
thrust is constant. It is burning fuel at a constant rate to produce that
constant thrust." is impossible, so the question is meaningless.

If the rocket car is experiencing constant thrust, it will accellerate
at a constant rate IF ITS MASS IS NOT CHANGING.

If it is burning fuel at a constant rate, and the thrust is constant,
then the accelleration would increase because the mass is decreasing.

I thought this got done with weeks ago.

I'll have to check google for that 'cause it's not in my seb headers
(I only pulled 100) I went ahead and did the total differential with
a changing mass (i think I left that out of the accel/velocity part)
and integrated that and ended up with a sum of 2 energies for the
total kinetic energy. I think that's what JT suggested I do (write
it wrt time)

One of the terms looks like it contains impulse and I forget what
you multiply impulse by to get E (I could have checked the
dimensions) but it looks normal.

Even if you skip the changing acceleration, the whole thing that
sticks out as bs to me is that LB thinks that linearly changing mass
and quad changing energy is wrong. That makes no sense. It's like
saying that linearly changing length should yield linearly changing
volume when we all know that volume will change cubically.

You can't blame Fred and John for launching through the roof with
that guy. (not that you did)
--
Best Regards,
Mike

Larry Brasfield · Mar 24, 2005

[Irrelevant and scurrilous subject revised.]

"Active8" <reply2group@ndbbm.net> wrote in message
news:195bgt3rf9uxe.dlg@ID-222894.news.individual.net...
[Old quote from a Brasfield post left as evidence.]

From: "Larry Brasfield" <donotspam_larry_brasfi...@hotmail.com
"Robert Monsen" <rcsurn...@comcast.net> wrote in message
No, as I recall, kinetic energy is 1/2 * m * v^2.
I recall seeing that claim from a high school physics teacher when
I was a smart-ass twerp. I posed the following puzzle to him:
A rocket car starts at rest, accellerating at a constant rate
because its thrust is constant. It is burning fuel at a constant
rate to produce that constant thrust. The kinetic energy of
the rocket car is allegedly M * V^2 / 2, so it is increasing
quadratically versus time. But the fuel consumed increases
only linearly with time. How can this be?

I would be interested in your take on this. My physics teacher
could not resolve it, (but, to his credit, that bothered him).
....
the whole thing that
sticks out as bs to me is that LB thinks that linearly changing mass
and quad changing energy is wrong. That makes no sense.

You are going beyond the evidence, pal. The
antecdote, relating to an event in 1967, bears
on my thinking at that time. To get from there
to "LB thinks" at this time, would required an
extremely limited view of my educatability and
surmises about intervening processes that go
way beyond the evidence. That is another
subject of course, and a silly one, so I do not
mean to get you going into it. (I won't follow
at any rate.) Perhaps, if you are willing to grant
me the provocatory status you did earlier, you
can see that what you call "bs" is just what you
suspected then.

I asked this before: How could it be a puzzle
without seeming to be "wrong" on its face?

I am puzzled as to why my puzzle puzzles you.
As I've said, it was proffered for fun. You seem
to have had fun with it. What is the problem?

It's like
saying that linearly changing length should yield linearly changing
volume when we all know that volume will change cubically.

I suppose you meant "linearly scaling an object in 3
dimensions" since what you actually stated is more
sensible with that substitution. So I am responding
to the statement you intended, not the one you made.

With that adjustment, I agree with you.

--
--Larry Brasfield
email: donotspam_larry_brasfield@hotmail.com
Above views may belong only to me.

Active8 · Mar 24, 2005

On Thu, 24 Mar 2005 11:31:41 -0800, Larry Brasfield wrote:

"Active8" <reply2group@ndbbm.net> wrote in message
news:195bgt3rf9uxe.dlg@ID-222894.news.individual.net...
[Old quote from a Brasfield post left as evidence.]
From: "Larry Brasfield" <donotspam_larry_brasfi...@hotmail.com
"Robert Monsen" <rcsurn...@comcast.net> wrote in message
No, as I recall, kinetic energy is 1/2 * m * v^2.
I recall seeing that claim from a high school physics teacher when
I was a smart-ass twerp. I posed the following puzzle to him:
A rocket car starts at rest, accellerating at a constant rate
because its thrust is constant. It is burning fuel at a constant
rate to produce that constant thrust. The kinetic energy of
the rocket car is allegedly M * V^2 / 2, so it is increasing
quadratically versus time. But the fuel consumed increases
only linearly with time. How can this be?

I would be interested in your take on this. My physics teacher
could not resolve it, (but, to his credit, that bothered him).
...
the whole thing that
sticks out as bs to me is that LB thinks that linearly changing mass
and quad changing energy is wrong. That makes no sense.

I asked this before: How could it be a puzzle
without seeming to be "wrong" on its face?

It wasn't wrong on it's face, but you asked him, "How can this be?"
It was a puzzle to you at the time.

I am puzzled as to why my puzzle puzzles you.

It was your confusion that puzzled me.

As I've said, it was proffered for fun. You seem
to have had fun with it. What is the problem?

You said, "I would be interested in your take on this." My take was
that I'd not have puzzled over it. IIRC kinetic E came before
conservation of momentum in the class and it was the latter subject
where change in fuel mass came up and then only in "The Physics
Problem Solver." I still didn't puzzle over it.

It's like
saying that linearly changing length should yield linearly changing
volume when we all know that volume will change cubically.

I suppose you meant "linearly scaling an object in 3
dimensions" since what you actually stated is more
sensible with that substitution. So I am responding
to the statement you intended, not the one you made.

With that adjustment, I agree with you.

So change the tense of "thinks" in:

the whole thing that
sticks out as bs to me is that LB thinks that linearly changing mass
and quad changing energy is wrong. That makes no sense.

and know that it was as much bs then as it is now.

Maybe I had fun with the total differential, but that depends on
what you consider fun. I'd call it interesting. Learning something
new is more fun.
--
Best Regards,
Mike

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