What is the direction of the buoyancy force?

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Discussion Overview

The discussion revolves around the direction of the buoyancy force and the reasoning behind it. Participants explore theoretical concepts related to buoyancy in fluids, with a focus on the implications of pressure variation and the behavior of objects in a fluid medium.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested
  • Homework-related

Main Points Raised

  • Some participants propose that the buoyant force acts upward through the center of gravity of the displaced volume.
  • One participant suggests that buoyancy can be conceptualized as a "hole" in the water or a negative weight, relating it to the weight of the water acting at the center of mass.
  • Another viewpoint considers a closed system of fluid and objects, arguing that the most stable state occurs when denser objects sink and less dense objects rise, leading to a configuration that minimizes the center of gravity.
  • There is a suggestion to refer to standard textbook derivations for the buoyant force, which indicate that the direction of the buoyant force is determined by pressure variation in the fluid.
  • One participant expresses skepticism about the original question being homework-related, while another questions the nature of the inquiry.
  • A participant mentions that water is heavier than air and speculates that pressure increases with depth in water might relate to buoyancy.
  • In response, another participant argues that since water is largely incompressible, the buoyancy of a given volume does not vary significantly with depth.

Areas of Agreement / Disagreement

Participants present multiple competing views on the direction and reasoning behind the buoyancy force, with no consensus reached on the underlying principles or explanations.

Contextual Notes

Some claims depend on specific definitions of buoyancy and pressure, and there are unresolved aspects regarding the implications of depth in fluid dynamics.

harvhk852
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What is the direction of the buoyancy force?
Why the buoyancy force acts in this direction??

Thanks for any help:smile:
 
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i believe the buoyant force acts upward through the COG of the displaced volume.
 
CPP is correct (welcome to PF, both of you!). As for why...um...it seems so straightforward it is tough for me to answer.

Consider a container full of water - its weight acts at the center of mass. Now empty the container, seal it, and submerge it in a larger container of water. You can almost consider buoyancy a "hole" in the water, or even kinda like a negative weight.
 
Another way to look at the same concept is to consider a given volume of fluid containing a given amount and type of objects as a closed system with a center of gravity. The most stable state for such a system is with the center of gravity at the lowest possible point (while still remaining a closed system). This only happens when the denser objects sink to the bottom and the less dense objects (less dense than the fluid) rise to the top.
 
harvhk852 said:
What is the direction of the buoyancy force?
Why the buoyancy force acts in this direction??
This looks like homework. Is it?

Look up the standard textbook derivation for the buoyant force. It clearly shows how the direction of the buoyant force follows from the variation of pressure in the fluid.
 
Gokul43201 said:
This looks like homework. Is it?

I doubt it's his undergrad thesis statement, so most likely
 
water is heavier than air, and i think it might have something to do with building pressure as you get deeper in water
 
Since water is largely incompressible, no, buoyancy of a given volume varies very little with depth.
 

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