Work calculation for lifting a Tetrahedron-shaped object from the water

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Homework Help Overview

The discussion revolves around calculating the work done in lifting a regular tetrahedron-shaped object from water using integrals. The original poster presents parameters including the tetrahedron's side length, water depth, and material density, while expressing uncertainty about their approach and seeking feedback.

Discussion Character

  • Exploratory, Assumption checking, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss the division of the problem into different regions based on the object's position relative to the water surface. There are mentions of calculating submerged volume, buoyancy, and the forces acting on the object. Some participants question the necessity of certain integrals and suggest alternative methods to avoid them.

Discussion Status

The discussion is ongoing, with participants providing guidance on using LaTeX for posting work and exploring different interpretations of the problem setup. There is no explicit consensus, but several productive directions have been suggested regarding the integration approach and the forces involved.

Contextual Notes

There are constraints regarding the format of submissions, as participants emphasize the importance of using LaTeX instead of images or PDFs. Additionally, the problem's requirement for integration is noted, though some participants suggest that standard results could be applied to simplify the process.

  • #31
@Frabjous, I tried sending a PM (private message) to you (and @NODARman). But the system wouldn't let me send it to you. I know the problem requires a method using integration, but If you are interested in how to do it without any explicit integration, let me know.
 
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  • #32
Steve4Physics said:
@Frabjous, I tried sending a PM (private message) to you (and @NODARman). But the system wouldn't let me send it to you. I know the problem requires a method using integration, but If you are interested in how to do it without any explicit integration, let me know.
If you are talking about not having to integrate 1-(h/h₀)³, I’d be interested.
 
  • #33
Frabjous said:
If you are talking about not having to integrate 1-(h/h₀)³, I’d be interested.
I'll attempt to send it again.
 
  • #34
Maybe I misread the above posts, but IMO the buoyancy (from Archimedes principle) needs to be ## \int \rho g \,dV=\int \rho g A \, dh ##. and note: ## \rho ## is the density of the water, so it along with ## g ## can be in front of the integral.). post 26 is trying to do an integral of ## \int V \, dh ## , and that is incorrect.
 
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  • #35
Charles Link said:
Maybe I misread the above posts, but IMO the buoyancy (from Archimedes principle) needs to be ## \int \rho g \,dV=\int \rho g A \, dh ##. and note: ## \rho ## is the density of the water, so it along with ## g ## can be in front of the integral.). post 26 is trying to do an integral of ## \int V \, dh ## , and that is incorrect.
It’s a work integral of a fully submerged volume. This is an incomplete thread because the discussion moved to a private conversation. I believe the OP is satisfied.
 
  • #36
Frabjous said:
It’s a work integral of a fully submerged volume. This is an incomplete thread because the discussion moved to a private conversation. I believe the OP is satisfied.
The OP looks to me to still be doing an incorrect computation of the buoyant force.
 
  • #37
Charles Link said:
The OP looks to me to still be doing an incorrect computation of the buoyant force.
He’s calculating the work done by gravity and buoyancy of a fully submerged constant volume that is lifted height L-h.
 
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  • #38
Frabjous said:
He’s calculating the work done by gravity and buoyancy of a fully submerged constant volume that is lifted height L-h.
Thank you=I just re-read the title of the post=the work to lift the object. I would expect to see ## W=\int F \cdot ds ##, but my mistake. :)
 
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