Re: Potentially painful

From: Robert Monsen (rcsurname_at_comcast.net)
Date: 03/09/05 

Date: Tue, 08 Mar 2005 22:33:56 -0800

John Larkin wrote:
> On Tue, 8 Mar 2005 12:44:56 -0800, "Larry Brasfield"
> <donotspam_larry_brasfield@hotmail.com> wrote:
>
>
>>"Robert Monsen" <rcsurname@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).
>
>
>
> At low velocities, a rocket is a very inefficient source of
> propulsion; at near-zero velocity, it's using its usual amount of fuel
> but hardly delivering any kinetic energy to the vehicle. As velocity
> increases, efficiency improves (or rather becomes less terrible) and
> vehicle energy accumulates faster. That trend continues until you run
> out of fuel.
>
> In a system that goes from extremely inefficient to only rather
> inefficient, it's not hard to shape the efficiency curve into a
> quadratic. A cog railway can be nearly 100% efficient, so it will need
> increasing amounts of fuel if it accelerates at constant gees, but
> anywhere on the path it will be a lot more efficient than a rocket.
>
> That make sense?
>
> John
>

Here is a web page written by somebody who has been driven insane by
this problem:

http://nov55.com/enrgy.html

His solution is that kinetic energy is really mv, not 1/2 mv^2. He has
equations and everything. Pretty wierd stuff. Who knows? 

-- 
Regards,
   Robert Monsen
"Your Highness, I have no need of this hypothesis."
     - Pierre Laplace (1749-1827), to Napoleon,
        on why his works on celestial mechanics make no mention of God.

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