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Questions tagged [buoyancy]

Use "buoyancy" for any question where an object is suspended or submerged in a fluid. Buoyant force is the force that acts upward on a partially or completely submerged object.

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What is the physical origin of buoyancy?

Imagine a horizontal cross-section $\Delta S$ of a cylinder containing a liquid of density $\rho$. The downward pressure on $\Delta S$ at the depth $d$ from the surface of the liquid is $P_{down}=\rho ...
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Buoyancy and Archimedes Principle [closed]

One kilogram of wood (density ~0.8 gm/cm^3) and 1 kilogram of aluminum (density ~2.7gm/cm^3) are dropped into a pool. Which has the largest buoyant force on it?
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Is there any weight diffenence between sealed/unsealed bottles? [closed]

I have to prepare my chemical report about CO2 molecular mass. I searched and got a sample report from internet. I read it and I can't understand this. Weight of flask covered with glass cover = ...
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Energy balance of this machine is positive. What is wrong? [duplicate]

Machine on this picture is inspired by video: https://www.youtube.com/watch?v=rxFXsoqbfrk There must be error in the computation of energy balance or there is another negative energy. Can you help ...
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Modell for the buoyancy of a hot air balloon

I was just working on a problem concerning a ballon for my introdouction to thermodynamics class. The helium ballon is emerged in air and surrounded by earths gravitational field, which shall be ...
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How do the principles of weather vane design change for underwater applications?

I am doing some research into the use of weather vanes under water. This "water vane" would serve the same function as a weather vane does in air, just while submerged in water. I understand that ...
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2answers
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Bouyant Force Confusion [closed]

I was asked to solve the question in the picture I naturally thought the answer was (1) because bouyant force is caused by the pressure difference on the object's top and bottom surfaces. Turns out ...
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1answer
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Bouyancy of ozone gas

If ozone is $O_3$ why is it an outer layer of the atmosphere? It seems $O_3$ would sink in a solution of $O_2$, rather than float on it.
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What are the horizontal forces on a heeling ship?

Consider the following image from Wikipedia: The article states: "Whenever a floating body in a liquid is given a small angular displacement, it will start oscillating about some point, called the ...
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1answer
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How can I get an idea of what is the volume of the air displaced by an object totally immersed in it?

My specific problem is that I can't figure out what object displaces more air, a rigid closed container or a similar container that is opened. For example, let's think in two similar bottles with ...
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1answer
68 views

How to calculate the normal force of a box in the bottom of a bucket of liquid? [closed]

I have been trying for some time now, and seem to be unable to come up with the correct answer. The setup for the problem is as follows: After finding a similar question and rechecking the buoyancy ...
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1answer
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How can one the find normal force of a block resting on a pool floor underwater?

There is the force of gravity on the block, the atmosphere, the water pressure o top of the block, but how about between the block and the floor? Would we calculate water pressure pushing up from the ...
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28 views

How do fluids behave in space with regards to bouyancy and density?

Will a fluid loose it's bouyancy in zero-gravity. What would happen if an object is immersed in a liquid in space (if the liquid is still very much together and not spilling as big bubbles or droplets)...
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1answer
51 views

Floating object and buoyancy force

A cubical object of side 100cm floats over a fluid of specific gravity 1.6. The depth of immersion is 75 cm. The centre of buoyancy lies 25 cm below the surface of the fluid. When measured from the ...
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Mathematical Demonstration of the Archimedean Principle [duplicate]

Can the Archimedes Principle be demonstrated mathematically?
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Which weighs more in atmosphere, $1\,{\rm kg}$ of steel or $1\,{\rm kg}$ of feathers?

I'm having a discussion at the moment regarding the mass of $1\,{\rm kg}$ of feathers and $1\,{\rm kg}$ of steel. The person I'm arguing with states that $1\,{\rm kg}$ of feathers will be lighter ...
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1answer
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Why the body is drowning in the swamp?

Is it correct explanation why does the body sink? Swamp is not a liquid, but particle suspension, that's why Archimedes principle not working and upward buoyant force not applied to the body.
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Can a battleship float in a tiny amount of water? [duplicate]

Given a battleship, suppose we construct a tub with exactly the same shape as the hull of the battleship, but 3 cm larger. We fill the tub with just enough water to equal the volume of space between ...
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Do the weights of two liquids not add when mixed?

I was given an interesting dilemma today. A co-worker saw me adding a liquid (Diisopropyl ethylamine AKA DIPEA) to a flask filled with another liquid (Tetrahydrofuran AKA THF). I needed to weigh out ...
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2answers
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Neutral buoyancy for cylinder/bladder in water

A 25 liter flexible plastic bladder consists of three parts: an air chamber located on top of the bladder, a large middle water chamber, and a lower weighted area that serves as a counterbalance and ...
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2answers
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What will happen to the level of water when the ice melts? [duplicate]

I have this:A piece of ice is gently placed on the surface of water filled in glass tumbler, so the water rises to the brim. What will happen to the level of water when the ice melts? I still don't ...
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3answers
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Attack point of buoyancy force

I have seen free body diagrams of submerged objects that show the buoyancy force acting on the centre of mass of the object. However, the buoyancy force arises due to pressure differences between the ...
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1answer
120 views

Initial acceleration concerning free fall

I'm in the process of conducting research concerning free fall with air resistence. I'm dropping a beach ball filled with air from certain heigts, while measuring its speed and acceleration during the ...
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2answers
72 views

Can you fill an aquarium with nitrogen? [closed]

My goal is to create an environment of nearly pure nitrogen where only anaerobes can survive. I need to be able to move samples in and out of it. How would you fill it? You can fill an aquarium with ...
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1answer
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Pressure increasing with depth work for directions other than downward

How does pressure increasing with depth work for directions other than downward? Can you explain this on the macro and micro level? I get how it works on a macro level for downward forces because ...
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Alternative forms of metacentric height based stability condition

For a floating body is stable condition Archimedes principle of buoyancy will be obeyed. where $M_{b}$ and $M_{w}$ are mass of the total body and mass of the emerged water. $$M_{b}=M_{w}$$ Tilting it ...
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1answer
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Buoyancy Confusion- What does the weighing scale show when a block is at the bottom of the beaker?

What does the weighing scale show when a block is at the bottom of the beaker? Is it equal to the weight of the beaker plus the weight of the mass? The issue I have with this is when a other scenarios ...
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2answers
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How do you explain the “weight” of helium?

If weight is measured as M * g (mass x gravity), then how does the "weight" of a massive helium filled balloon negative? Let's say you have a 63,000 m^3 helium balloon. The mass of the helium is ...
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1answer
40 views

Does buoyant force become less effective as acceleration increases?

Lets say a balloon with a certain amount of buoyant lift has a 2 kg mass strapped to it (including engines) and accelerates enough that it perceives a positive 2.5 g inertial force (2.5g * weight) ...
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1answer
35 views

How does buoyant force react with an acceleration $g$ load?

If a blimp with a certain amount of helium buoyancy accelerated enough to perform, let say, a +2G maneuver, would the buoyant helium force scale along with the weight force? All the mass particles ...
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1answer
80 views

Movement of a helium filled vs lower-density-gas filled balloon inside an accelerated car

It's well known that a helium balloon inside of a car moves forward when the car accelerates, and backward when it slows down. What would happen, though, if a lower density gas was used instead of ...
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4answers
161 views

Wood in water and buoyant force

Wood doesn't sink in water because its density is less than water density. So $ΣF=0$. But what is the force that counterbalances the gravitational force if the wood does not sink in water so that ...
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How do you calculate the rate of ascent for frozen seawater in seawater?

Assuming 1m3 sphere of seawater were flash frozen at a depth of 1km, how rapidly would it start ascending to the surface given the buoyancy? Assuming we could ignore bonds between the surface of ...
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Gravity and objects in substances

This is probably a matter of terminology and me not finding it due to the lack of it. An apple falls from a tree on the ground due to gravity. Yet, if it falls into a water pit it floats on top of ...
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2answers
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Buoyancy force on object between three liquids

I have a thought experiment. Suppose you have 3 layers of liquid resting on each other in a beaker. A long cylinder of some material is placed in the beaker so that it passes through all layers of ...
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1answer
149 views

How to calculate speed of buoyant object rising

I'm looking for a formula to calculate the speed of object in buoyancy. Is there any formula available for this purpose? For example, if I release one liter water bottle from under 10 meter distance ...
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1answer
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Pressure exerted by a liquid on the bottom of a submerged object [duplicate]

I understand that pressure increases with depth in a liquid and that it is the difference in pressures at the top and bottom of an object submerged in a liquid that provides the buoyant force. What I ...
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48 views

Balloon rising up in water and reading on the scale

The balloon rises beause of buoyant force being greater than its weight, I'm interested in the change in scale reading while the balloon is still completely underwater. And let's ignore any viscous ...
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118 views

Does a Helix shaped object floating in water stream rotate?

A Helix shaped light weight object is placed a water stream. Does it rotate? It is pushed by water body, will it also experience turning force and thus rotate?
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How buoyancy and convection are related?

If I'm not wrong buoyancy formula is $$F_{B}=\rho gv_{sub}$$ In convection it is said that fluids with less density come up and parts with lower density ,which are cooler , go down and this cycle ...
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Why oxygen bubbles are larger than hydrogen bubbles during water electrolysis?

During water electrolysis, I found the oxygen bubbles are usually larger than the hydrogen bubbles. I think the reason is because different gases have different contact angles. The contact angle of ...
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2answers
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Point of application when the force is the up thrust?

We have been taught that the point of application is the point at which the force is applied. In contact forces, the point of application is the point of contact and in forces acting from a distance, ...
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Is it possible to make a vacuum balloon filled with electromagnetic radiation float?

Given the right materials and structure, could you theoretically use radiation pressure to keep a equilibrium amount of pressure inside a special vacuum balloon so that it would float. (ignoring the ...
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If I jump from space using a spacesuit filled with hydrogen could I survive the fall? [closed]

If I fill a spacesuit to its maximum volume with hydrogen while wearing it (who cares about the breathing part anyway) and jump from space (let's say, from 100km above sea level, a.k.a. Karman Line), ...
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1answer
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Determine velocity of balloon from known Buoyancy, mass and surface [closed]

I need to know how to get velocity of weather balloon, if I know it's buoyancy force, mass and surface(diameter). I am using now $$v = 0.5t\left(\frac{F_\text{all}}{m}\right),$$ [$m$ = mass, $v$ = ...
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73 views

Are these sandals floating due to surface tension or buoyancy?

Having an argument. If the sandals are wet (which I think we can assume they are), then they have broken the surface, correct? And if they’ve broken the surface, then that leaves only buoyancy to hold ...
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Why does not a bubble in a thick hand sanitiser not rise?

Here is a picture of a bubble trapped inside a thick hand sanitiser. These bubbles never rise despite not sticking to the walls! They just remain stationary, in the middle of the liquid, despite the ...
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Can ants walk on liquid mercury? [closed]

I'm not a physicist, but I was wondering: Can ants walk on dense liquid like mercury and why?
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335 views

Why can't hot air balloons fly higher then helium balloons?

I have read these questions: Hot air balloon trajectory predictions Do atmospheric physics prevent hot air balloons from ascending over 60,000ft? What is precisely the reason that a helium balloon ...
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Confusion on center of movement while tilting a floating body

When a floating body is tilted at an angle $\theta$, the restoring moment will be about the metacenter. But is the tilting movement about the center of gravity? If it is, then it looks like there ...