Re: Energy, etc

[brian whatcott <inet@INTELLISYS.NET>]

At 09:16 8/6/99 +1000, Brian McInnes wrote:

> there are three external forces acting on the person....
> - the gravitational force
> exerted by the earth on the person and the contact force exerted by
> the floor.  The third force is the normal contact force exerted by the
> wall on the person.  As long as the person is in contact with the wall
> there is no relative movement between that force and its point of
> application and so that force does no work on the person.

> All the other movements are internal to the articulated person and do
> not do work on the person, no more than do the various linkages in an
> automobile do work on the automobile as it starts its journey.  The
> changing in effective horizontal length of the arm during the push is
> a necessary part of the mechanism that is resulting in changed motion
> of the person.
>
> To take the story a little further the change in the person's kinetic
> energy is associated with a loss in chemical energy....
> Brian McInnes
This commentary is recognizably similar to one I read from a NASA
contributor who mentioned the megawatts of power developed by the
LOX pumps as the shuttle lights off at the dock.

(It is necessary to pump great masses of fuel and oxidizer into the
combustion chamber which develops the pressure needed to eject
 the rocket efflux.)

 One mentioned that at the initial hover, the shuttle was providing
 no external work at all.



brian whatcott <inet@intellisys.net>
Altus OK