I Question Regarding Force Being Equal, Even Moving Upwards (if V=0)?

AI Thread Summary
The discussion centers on the confusion surrounding force application when lifting versus lowering a heavy object at constant velocity. While the physics equation F = ma indicates that the forces balance out to zero in both scenarios, the perceived effort differs significantly. Raising a heavy slab requires more energy than lowering it, despite both actions involving the same force according to physics. This discrepancy arises from the complexities of human physiology and the nature of work done, where raising an object involves positive work and lowering involves negative work. Ultimately, understanding force requires acknowledging that human perception and physical effort do not always align with theoretical physics.
Ascendant0
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I understand based on the equation F = ma that if there is no acceleration, the forces on the object all balance out to 0 in all directions.

What I don't get is for example, slowly lowering a heavy stone slab at a constant velocity v, and raising it way above my head as high as I can at a constant velocity v, would be considered to be the same force (since my force on it would be equal to the normal force since there's no acceleration). Obviously, it's going to be a LOT harder raising that stone slab overhead as it would be slowly lowering it. It would take a lot more effort, yet according to the force equation, I'm still applying the same force. That to me is a bit confusing.

I'm thinking I'm just viewing "force" conceptually wrong here, but if someone could help me make more sense of why this is the case in the above example, I'd greatly appreciate it.
 
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Ascendant0 said:
It would take a lot more effort
Your perceived effort is a very poor measurement of force. It is exceptionally difficult for humans to do constant velocity motions or to accurately gauge the force applied during different movements. The perceived effort will also involve the motion of your own body, not just the external object.

You should always avoid human-perception based explanations. Replace a human with a spring or something similarly easy to analyze. A spring will elongate by the same amount if you are raising or lowering a mass at constant velocity.

In short, the physics definition is correct, but humans are complicated.
 
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Ascendant0 said:
I'm thinking I'm just viewing "force" conceptually wrong here,
Correct. At the very least, you have to consider the work done, which is positive when raising something, and negative when lowering something at constant speed.

However, for physiological reasons, doing negative work with your muscles doesn't recharge your body (like regenerative braking would). You still consume energy, and it might even be more exhausting to your muscles to operate like this.
 
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