Question about the Archimedes principle and gravity.

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Discussion Overview

The discussion revolves around the implications of Archimedes' principle and the concept of weight in different environments, particularly comparing Earth with an atmosphere to a hypothetical planet with the same gravity but no atmosphere. The scope includes conceptual understanding and practical applications in engineering and physics.

Discussion Character

  • Conceptual clarification
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions whether objects on Earth would be lighter due to the buoyant force of the atmosphere compared to a similar planet without one.
  • Another participant clarifies that while mass remains constant, the buoyant force affects weight measurements in fluids, providing an example involving scales in water.
  • A follow-up response suggests that air does exert a buoyant force on objects, similar to water, and questions the practical implications of this effect in engineering and physics measurements.
  • Some participants note that mass is measured differently and that real-world differences in weight due to buoyancy are negligible for most engineering applications, unless specifically exploiting the effect.

Areas of Agreement / Disagreement

Participants express varying views on the significance of buoyancy in weight measurements, with some suggesting it is negligible in practical scenarios while others emphasize its conceptual importance. No consensus is reached on the necessity of accounting for buoyancy in engineering practices.

Contextual Notes

Participants mention that the differences in weight due to buoyancy are small and may not need to be considered in most engineering contexts, but this remains a point of discussion regarding specific applications.

DrSmersh
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Hello, I was taking a shower and started to think about balloons and helium and this question came to me:
Wouldn't the things on Earth be lighter than say, a similar planet (same gravity) but with no atmosphere? (because of the push from air)
I googled it but I am not sure of using the correct keywords.
PS: I am starting engineering and my physics knowledge is not very superior to an AP level (I don't really know how to compare our educational systems sorry :P)
 
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That depends on exactly what you mean by weight. They will have the same mass, and experience the exact same amount of force downward, but without a fluid surrounding them the effect of buoyancy will not exist.

Consider this. If I put a scale at the bottom of a pool, you will weigh less inside the pool than outside according to the scale. However if I put both you and the pool onto a scale, your full weight will show.
 
Drakkith said:
That depends on exactly what you mean by weight. They will have the same mass, and experience the exact same amount of force downward, but without a fluid surrounding them the effect of buoyancy will not exist.

Consider this. If I put a scale at the bottom of a pool, you will weigh less inside the pool than outside according to the scale. However if I put both you and the pool onto a scale, your full weight will show.
Thanks for the reply
Considering that air pushes a balloon I assume that it is a fluid, I mean it has the bouyancy effect on everything in the atmosphere. We might not float but we weight less (like a rock under water) if we compare us standing on a scale in a similar planet (equal gravity), is that correct?
So in all the exercises that i did when practicing Newton's laws the result in real life should be different partialy because of this airpush? I suppose the difference would be very small then, but does a civil engineer have to take that in account when building a bridge or any structure for example? Or a phyisist when trying to measure the as close to real as possible mass of a particle or element (I don't know how they measure this things but suposing that in some part of the process they have to weight something and decompose the forces that are presented)?
 
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Mass is measured differently, so we don't really have to worry about that. Plus, if you REALLY want to measure the weight of an object, just take it into a vacuum chamber. In any case, the real world differences are so tiny that in practically all cases you don't need to take them into account in order to build anything. (Unless you are trying to exploit the effect of course)
 
Drakkith said:
Mass is measured differently, so we don't really have to worry about that. Plus, if you REALLY want to measure the weight of an object, just take it into a vacuum chamber. In any case, the real world differences are so tiny that in practically all cases you don't need to take them into account in order to build anything. (Unless you are trying to exploit the effect of course)

Awesome thanks, that answers my question.
 

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