Does an object's kinetic energy increase, decrease, or stay constant when it reaches terminal velocity while falling?
Assuming that the terminal velocity doesn't change during the fall, then the kinetic energy would remain constant. However the terminal velocity decreases during the fall since the air becomes denser at lower altitudes. Hence the speed and the kinetic energy of the falling body would both start to decrease after reaching the altitude where the terminal velocity is lower than the object's vertical velocity.
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