Originally Posted by
Ian W
A^2 I think you are getting carried away with the turns being air radius turns and forgetting your basic physics the the aircraft is actually ground referenced, for acceleration and deceleration.
1, Take a 3 ton weight that is stationary that then turns along a rate 2 turn radius and accelerates to 120kts in 30sec
2. Take a 3 ton weight that is traveling at 120kts that then turns along a rate 2 turn radius and decelerates to stationary in 30sec
Your argument is neither of these weights experience any acceleration. I say that is obviously false.
My understanding is that the force in the turn to hold the weights in the turn (centripetal force ꟺ) accelerates the weights as it is (as you say) a change in velocity that can only come with application of a force. The ground radius described by a slow moving (compared to the wind) aircraft in an air radius turn is uneven stretched by the wind velocity vector. In consequence the centripetal force ꟺ to accelerate the aircraft (to change its velocity vector ) is uneven. An aircraft with a tight ground radius first being accelerated more at first while the aircraft with a wide ground radius first is accelerated less at first. These ꟺ accelerations - changes in velocity vector - must be added to the ground speed accelerations (decelerations) These differences will only really be apparent when the wind velocity is close to or a large fraction of the aircraft velocity.
Ian,
You've made the same fundamental error- and you've been arrogant with it.
Before saying someone has forgotten basic physics, you'd best learn some yourself.
The earth is not a privileged frame of reference and no, no value HAS to be calculated in reference to it. All calculations of velocity, acceleration and therefore momentum and kinetic energy work in any frame of reference- as long as you STAY in one frame of reference.
Momentum is not related to groundspeed. It is related of whatever frame of reference you choose to calculate in.That is implicit in Newtons first law of motion,