What is Bouyancy: Definition and 53 Discussions

Buoyancy (), or upthrust, is an upward force exerted by a fluid that opposes the weight of a partially or fully immersed object. In a column of fluid, pressure increases with depth as a result of the weight of the overlying fluid. Thus the pressure at the bottom of a column of fluid is greater than at the top of the column. Similarly, the pressure at the bottom of an object submerged in a fluid is greater than at the top of the object. The pressure difference results in a net upward force on the object. The magnitude of the force is proportional to the pressure difference, and (as explained by Archimedes' principle) is equivalent to the weight of the fluid that would otherwise occupy the submerged volume of the object, i.e. the displaced fluid.
For this reason, an object whose average density is greater than that of the fluid in which it is submerged tends to sink. If the object is less dense than the liquid, the force can keep the object afloat. This can occur only in a non-inertial reference frame, which either has a gravitational field or is accelerating due to a force other than gravity defining a "downward" direction.Buoyancy also applies to fluid mixtures, and is the most common driving force of convection currents. In these cases, the mathematical modelling is altered to apply to continuua, but the principles remain the same. Examples of buoyancy driven flows include the spontaneous separation of air and water or oil and water.
The center of buoyancy of an object is the center of gravity of the displaced volume of fluid.

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  1. C

    Solving the Mystery of a Floating Bottle: Density & Volume

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  2. M

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  3. B

    B Buoyancy thought experiment

    If we place a cork in a beaker then filled the beaker with normal-sized marbles, the cork will remain stationary at the bottom of the beaker. However, if we continuously decrease the size of the marble, at a certain point, the marbles will behave like a liquid and the cork will rise to the top...
  4. N

    Bouyancy Question: Two weights on strings, with one weight submerged

    Hi new to the physics world and the symbiology is hard to understand completely. Attached is the work I've done to a final solution but I can't seem to get the answer in terms of only density of water and T1 and T2. Thank you for any assistance. [ Mentor Note -- Word file replaced with a...
  5. T

    Bouyancy force -- What mass can the balloon carry?

    In a I used FBouyancy - FBalloon -F mass = 0 rewrote mass as a product of density and volume to obtain; m= v(densityair - densityHe) m= 1031.5kg.I am stuck in part b. I have this formula called Barometric formula which ı should use; P = P0 * e((-P0*g*h)/ P0 So what I understood is that...
  6. L

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  7. BethNB

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  8. C

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  9. Adam Rabe

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  10. KeiaYamada

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  11. Ian Baughman

    I Buoyant Force and what densities to consider?

    So I know FB = ρDF × g ×VDF when we submerge an object in a fluid such as water but what if we were talking about a hot air balloon? In this case would it be correct to use FB = (ρin - ρout) × g ×Vobject? Where ρin = density inside balloon and ρout = density outside balloon. If this is...
  12. physicist007

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  13. S

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  14. S

    Floating block with objects that are thrown in a liquid

    Homework Statement I'm confused about the following kind of situation. Consider a block of density ##\rho_b##, mass ##M_b## and section ##S_b## that floats on a liquid of density ##\rho_l##, in a tank of section ##\mathcal{S}##. On the block there are some objects (all equal), of density...
  15. SadPanda6022

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  16. UMath1

    I Force applied to a fluid

    If you place an solid object on a fluid, is the force it applies to the fluid equal to the buoyant force? I would have thought that it applies a force equal to its own weight but that would mean that the force applied to the object by the fluid, the buoyant force, would not be equal and opposite...
  17. S

    Buoyancy With Solid Sphere

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  18. L

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  19. H

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  20. A

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  21. H

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  22. M

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  23. J

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  24. N

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  25. S

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  26. P

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  27. B

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  28. A

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  29. M

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  30. P

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  31. R

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  32. R

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  33. Z

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  34. U

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  35. W

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  36. G

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  37. T

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  38. K

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  39. R

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  40. H

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  41. C

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  42. S

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  43. C

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  44. R

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  45. F

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  46. D

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  47. C

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  48. D

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  49. C

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