Measuring Buoyancy: How to Calculate Upward Force

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Discussion Overview

The discussion revolves around calculating and measuring the buoyant force experienced by objects, specifically using a beach ball as an example. Participants explore the relationship between the volume of the object, the weight of the displaced fluid, and the factors affecting buoyancy, including the viscosity of the liquid and the compressibility of the object.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant questions how to determine the upward buoyant force based on the volume of the object and the viscosity of the liquid, suggesting that the force to push the beach ball underwater might equal the weight of the displaced water.
  • Another participant seeks clarification on whether the inquiry is about calculating or measuring the buoyant force, referencing Archimedes' principle in the context of calculation.
  • A later reply confirms that the force to push the beach ball underwater is indeed related to the weight of the displaced water, noting that the weight of the beach ball itself is negligible.
  • Another participant adds that for accurate calculations, the weight of the beach ball should be subtracted from the weight of the displaced water, while also mentioning that the compressibility of the beach ball affects the volume of water displaced.

Areas of Agreement / Disagreement

Participants generally agree on the relationship between the buoyant force and the weight of the displaced water, but there is no consensus on the specifics of measurement and the impact of the beach ball's compressibility.

Contextual Notes

Participants express uncertainty regarding the extent to which the compressibility of the beach ball affects the volume of water displaced, and there are unresolved questions about the best methods for measuring buoyant force.

thetexan
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When I take a beachball and force it underwater it is almost impossible due to the upward force of the buoyancy. Is there a way to determine what that upward force is based on volume of the object, or viscosity of the liquid (including air and balloons).

How does one figure that? Since the weight of the object being "floated" is equal to the volume of the water displaced wouldn't the force to push the beach ball underwater equal to the weight of the water displaced by the ball in units of force instead of weight?

tex
 
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thetexan said:
When I take a beachball and force it underwater it is almost impossible due to the upward force of the buoyancy. Is there a way to determine what that upward force is based on volume of the object, or viscosity of the liquid (including air and balloons).

How does one figure that? Since the weight of the object being "floated" is equal to the volume of the water displaced wouldn't the force to push the beach ball underwater equal to the weight of the water displaced by the ball in units of force instead of weight?

tex

Your question is confusing. Are you looking for a way to calculate the buoyant force, or are you trying to find a way to measure the buoyant force?

If the former, then I'll first ask you if you are familiar with Archimedes principle. If it is the latter, attach a spring to the balloon the measure the pull on the spring when they are all under water.

Zz.
 
thetexan said:
wouldn't the force to push the beach ball underwater equal to the weight of the water displaced by the ball
Yes (minus the weight of the ball, negligible for a beach ball).
 
The calculation of the weight of the displaced water should be about right. If you want accuracy, weigh the beachball and subtract it. Remember that the beachball is compressible, so it will displace less water than if you measure it's size in the air. (I don't know how big the difference is.)
 

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