Conceptual Question about Buoyancy

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    Buoyancy Conceptual
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Discussion Overview

The discussion revolves around the concept of buoyancy, specifically comparing the buoyant forces acting on two identical objects submerged in different fluids (freshwater and glycerine) and the implications of these forces when the objects are floating versus fully submerged. The scope includes conceptual reasoning and exploratory questions related to buoyancy and fluid mechanics.

Discussion Character

  • Exploratory
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant suggests that since both objects are of the same mass and volume and are floating, the buoyant forces acting on them must be the same.
  • Another participant notes that the waterline and glycerin line will differ, implying that the volumes of fluid displaced will not be the same, even if the buoyant forces are equal.
  • A scenario is proposed where the objects are fully submerged in their respective fluids, questioning whether the balance of scales would change and if the buoyant forces would remain the same.
  • Some participants express their reasoning that the balance of the scales would not change because the displaced fluid remains in the buckets, maintaining equal mass.
  • There is a prompt to consider the buoyant force on each submerged mass and whether it is the same for both fluids.

Areas of Agreement / Disagreement

Participants express differing views on whether the buoyant forces are the same in different fluids and whether the balance of scales changes when the objects are submerged. The discussion remains unresolved with multiple competing perspectives.

Contextual Notes

Participants have not reached a consensus on the relationship between buoyant force and fluid type, nor on the implications for the scales when the objects are submerged. Assumptions about the behavior of fluids and buoyant forces are not fully explored.

jayadds
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Say that I have two objects of the same mass and volume. I place one into freshwater and another in glycerine. In both cases, the objects are floating. Would the buoyant force from both of these fluids acting on the object be the same?

From my understanding, buoyant force measures the weight of an object if it's floating. Since both of the objects are of the same weight and are afloat , does it make sense to think that the buoyant force would be the same in the two situations?

Many thanks.
 
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jayadds said:
Say that I have two objects of the same mass and volume. I place one into freshwater and another in glycerine. In both cases, the objects are floating. Would the buoyant force from both of these fluids acting on the object be the same?
Yes.

Since the objects are floating, the buoyant force must equal the weight.
 
Note that the waterline on the hull will not be the same as the glycerin line. I.e. They will displace different volumes of fluid to get the same buoyant force.
 
Now imagine the two identical objects are not floating, but hanging on a scale like this:

waage_f1c.jpg


Your water and glycerin are in buckets standing on a scale like this:

scale.gif


Both scales are initially balanced. Then you submerge the objects into the buckets, and they do not float, but submerge fully (without touching the walls).

Does the balance of the scales change? If yes, how?
 
A.T. said:
Now imagine the two identical objects are not floating, but hanging on a scale like this:

waage_f1c.jpg


Your water and glycerin are in buckets standing on a scale like this:

scale.gif


Both scales are initially balanced. Then you submerge the objects into the buckets, and they do not float, but submerge fully (without touching the walls).

Does the balance of the scales change? If yes, how?

Hmm...that's a really good question. I would think that the balance of the scales would not change. This is because the displaced fluid from the fully submerged object does not escape from the buckets and thus, the mass in both of buckets remain equal when the objects are added. This is just my thinking though. Is this correct?
 
jayadds said:
Hmm...that's a really good question. I would think that the balance of the scales would not change. This is because the displaced fluid from the fully submerged object does not escape from the buckets and thus, the mass in both of buckets remain equal when the objects are added. This is just my thinking though. Is this correct?
Consider the buoyant force on each submerged mass. Is it the same for each?
 
jayadds said:
Hmm...that's a really good question. I would think that the balance of the scales would not change. This is because the displaced fluid from the fully submerged object does not escape from the buckets and thus, the mass in both of buckets remain equal when the objects are added. This is just my thinking though. Is this correct?
Try to figure out the upper scale first, where the objects hang, and consider what DocAl said.
 

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