Calculating Work, Energy, and Power: Integrating Force and Velocity

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Homework Help Overview

The discussion revolves around calculating work, energy, and power in the context of a rope being lifted. Participants explore the integration of force and its relationship with velocity, questioning the assumptions made in the problem setup.

Discussion Character

  • Exploratory, Assumption checking, Conceptual clarification

Approaches and Questions Raised

  • Participants discuss integrating force to find work done and its relation to power, with some questioning the validity of the original poster's approach. There is debate over whether to apply the work-energy theorem or conservation of momentum, with various interpretations of energy transfer and losses being explored.

Discussion Status

The discussion is active, with multiple perspectives being shared. Some participants provide guidance on considering different physical principles, while others express uncertainty about the assumptions being made regarding energy conservation and the behavior of the rope.

Contextual Notes

There are indications of missing information regarding the system dynamics, particularly concerning how energy is distributed during the lifting process and the effects of oscillations in the rope. Participants also note the potential for energy loss in various forms, complicating the analysis.

  • #31
Delta2 said:
Ok I see and then we arrive at the answer you post at #2, which differs by a factor 1/2 on the first term from the book answer. Well, it beats me, according to your opinion why it differs? OK I know that conservation of energy does not hold always but why using the momentum approach we still don't get the right answer cause as you say the right answer will be something in between?
Maybe the flaw in the momentum calculation is P=Fv. The element being accelerated from rest only averages v/2 in that process, so it should be P=Fv/2.
 
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  • #32
I think I like it. And if there are discrete lengths (like a chain link) there will be some fluctuations but the average work will be as you say. And if we allow other degrees of freedom to bleed off the speed during this process we end up with drag forces which I am certain will be difficult to characterize and more difficult to quantify.
 

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