Originally Posted by
bearfoil
If unaccelerated?
The aerodynamic braking during airplane controlled descent consumes the gain of Kinetic Energy, resulted from the Ep to Ek conversion, resulted from the loss of height/elevation. Slowing down for landing, means decreasing the Ek. What is left of the Ek, at touch down, is consumed (converted into other forms of energy) further through aerodynamic and mechanical braking.
The Ep to Ek conversion takes place regardless of controlled descent, or free fall. The difference is that in a free fall the Ek gain (or most of it, to be accurate) is not consumed/converted until the very end of the descent.
The airplane case is not different than a car descending a hill, from the generic Ep to Ek conversion perspective.
A car's free hill descent, will mean gain of speed - Ek not consumed. A controlled descent at constant speed, or decreased speed, requires different degrees of braking. The braking is consuming the Ek gain through friction, converting into Thermal Energy - brakes are quite hot at the bottom of the hill.