"Cynic" <cynic_999@yahoo.co.uk> wrote in message 
news:vorjr2tm42otvrrir79s867g86kr167l3k@4ax.com...
> On 25 Jan 2007 08:02:19 -0800, google@woodall.me.uk wrote:
> 
> > So I did the (simplest) calculations with the engine in the rocket and
> > showed that the energy required was exponential in the rockets final
> > speed.
> 
> No you did not!!!  The only reason that the fast rocket requires more
> energy is because it has more mass, and therefore the same force will
> produce a weaker accelleration.  As I said and you ignored, do the
> same calculations using a fuel with an extremely low mass (but equal
> thrust), or (preferably) ignore the loss of fuel mass altogether for
> the purpose of the thoiught-experiment because that factor has nothing
> to do with your assertion.
> 
> As for the amount of energy required being dependant upon the distance
> travelled, that is clearly a nonsense.  Accellerate the rocket to
> 1000MPH and then cut the engine.  The total energy is the same whether
> the rocket thereafter travels for 10 miles or a million miles.

Actually I think you make an error here, the same error I made, and many
people make, you only couont the distance travelled whilst the force is 
applied.

However again, you (and I may be correct) - it depends (I think).

It depends if you are on the rocket or if you are a stationary observer at 
the start
point!!

Don't worry I am still trying to get my head around it myself!!

I will get back about the matter later!!


> 
> --
> Cynic
>