Why airplanes taxi

Gee, where would the energy come from to cause the acceleration?

On Feb 6, 2:00*pm, Mxsmanic wrote:
writes:
And to answer your next post before you post it:

What molecules?

http://en.wikipedia.org/wiki/Outer_space

"While not being an actual perfect vacuum, outer space contains such sparse
matter that it can be effectively thought of as one. The pressure of
interstellar space is on the order of 10 pPa (1×10-11 Pa)."

So, no molecules. *And no friction.

Even if you don't wish to consider the hard vacuum of space as perfect, with a
pressure that is 10,000,000,000,000,000 times lower than that of Earth at sea
level, the friction should be also that much lower, and thus the speed of a
taxi should be trillions of times faster. *The speed of light is only fifteen
million times faster than a 40-knot taxi, so nearly the speed of light might
well be achieved long before any residual friction could have any effect.