RE: [Paddlewise] Paddling in Space

Ron Dunnington writes: 

"A rocket engine does not push against anything
except the rocket body and that is why it can operate with, or without an
atmosphere, or, even in water. A paddle must have something to push against
(more like a jet engine than a rocket), to be effective. "

That's sort of my point.  Rocket engines work on Newtonian principles --
very light particles of rocket exhaust accelerated to extreme speeds
generates Newtonian thrust without anything to push "against."

Paddles work more like wheels -- the paddle pushes against the friction of
the water to move the kayak forward, relying much less on Newtonian reactive
forces.

Of course, all this intergalactic thinking has made me realize the error of
my earlier post.  The entire universe is Newtonian.  When I accelerate my
car, I must be imparting a certain (very small) acceleration to the spin of
the earth as an equal and opposite reaction to the force of acceleration for
my car.  Of course, it doesnt matter much to me whether I get where I am
going by moving my car to my destination, or spinning my destination closer
to my car!  I guess this proves Nick's point that moving a large mass a
little bit is more efficient (in Newtonian terms) than moving a small mass
very fast.

But when paddling, moving water backwards is wasted energy.  It is
inevitable, but the less energy absorbed by the movement of water, the more
energy is put to moving the kayak forward.  So slippage, while inevitable,
cant be a good thing . . .

--Karl Coplan
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