<span>Transitional environments</span>
The correct answer to the question above is 20 millibar pressure difference between two near locations. The highest surface winds speed occur when there is a 2- millibar pressure difference between two nearby locations. Wind speed or also called as wind velocity is caused by the higher air pressure going to low.
(if it's frictionless the length doesn't even matter :) )
It would have the same kinetic energy down as the potential energy up. That is,

or

(the mass doesn't even matter). The result is

, so only the height matters really. It is almost 9 (it is

).