https://www.khanacademy.org/science...and-energy-tutorial/v/work-and-energy--part-2 I was watching a video at Khan Academy on Work & Energy (link above). At 2:50, he describes a situation with an elevator doing work against gravity. My question is pretty simple: If the acceleration (and hence, net force) is equal to zero (the upwards force cancelling out the downwards force due to gravity), how did the upwards force produce any movement at all? The constant velocity means there's no acceleration, and that's fine. But shouldn't there be no movement at all? eg. [let down be negative] If I hold my hand out and apply an upwards force of F=mg, wouldn't that merely counteract downwards acceleration due to gravity (F=-mg)? Wouldn't my hand merely stay still in the vertical plane? Or, in a similar example more related to the one in the video, if my hand was held out and accelerating upwards due to a force, and that force changed to be equal and opposite to the force of gravity, would my hand continue to move upwards (with zero acceleration) at a constant velocity? This is a conceptual problem that's been bugging me... even though the math supports what coursework teachers. I need help grasping this concept.