wrote in message
...


OTOH energy does not
cancel itself out, as "Charles Momsens" first post seems to suggest.

DSK

I'll refer you to the Poynting Vector of the near field of an antenna. The
vector shows at different times an energy flow away from the antenna and
towards the antenna. The net energy flow over time is zero. It depends how
one measures energy, in that example measured over time across a surface it
indeed cancels with each cycle of the electromagnetic wave.

An tangential electric field impinging onto a metal surface is driven to
zero by the reaction of the conductor, the energy is cancelled - driven to
zero since the electric field is zero by the reaction of the conductor.

Magnets stick to each other with opposing polarity - driving the net field
to zero, hence its energy. Same with charge.

Take the electron orbiting the atom. The electron is in a circular orbit,
which by definition is an acceleration. An accelerated charge radiates. So
if the electron is radiating, over time the orbit should collapse since the
energy sustaining its orbit is radiated. Yet the electron does not collapse,
atoms have been around a very long time. That's because the energy radiated
by the electron alters between 2 types of field and the energy that would
have been radiative ends up cancelling itself and is not radiated. This
condition only occurs under particular orbital path lengths (orbits are
quantized for a reason, if the orbit is not following the correct quantized
path then the atom radiates - light, heat, x rays, radio waves, etc and the
atom goes to a new energy state or separates in constituent parts).


Energy has amplitude, phase, location, direction and exists over time, it
certainly can cancel itself out. If it didn't atoms would not exist. Can you
name a natural system that doesn't drive itself to the point of lowest
energy?

In a macroscopic sense, on a large scale bulk measurement mechanical energy
does not tend to cancel itself out. On the atomic or quantum level it can
very well cancel itself out, as well on large scale electromagnetic
phenomena.


In the propeller example what force is exerted in the direction of the
torque vector? None, the forces that create the imaginary convention of
torque vector are at right angles to it. The unit of the torque vector is
not force. The torque vector and thrust lay along the same axis, but thrust
is a force and the torque vector is an imaginary convention. The forces
creating the torque vector is at right angle to the thrust. It's not even a
question - it was jibberish. Ian is correct.

Torque vector is not synonymous with "torque" as it is commonly used or
understood.