# 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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### Which tube experiences a larger buoyant force?

I saw lots of debate about this question. Some are saying that this cannot be solved because the weight of the tubes is not given. Others say the red one experiences more buoyant force because for red:...
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### Buoyancy versus viscosity

A common problem in casting is removing the air bubbles that might might be in the mold material, like plaster or resin. This is typically done by degassing--putting the mold material under vacuum to ...
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### What is the feasibility of a ropeway pulling airships?

At a steady walking speed, a horse can move approximately fifty times as much weight in a boat as it could with a cart on old-fashioned roads. How much could one HP move if the load was free floating ...
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### Related bubble questions: In water vs air, what causes bubbles to form?

One thing I would guess would happen is that air released under water would diffuse through it as individual molecules rather than collecting as bubbles. I suspect the bubble effect might come from ...
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### A Question What is wrong in my Gedankenexperiment? about the Conservation of energy [closed]

Please excuse my English... Let's say we have a 10m x 10m x 10m water tank filled with water. After a little search i found that the pressure on the sidings at 9-10m depth would be approximately -> ...
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### Why does weight increase if an object is held in water?

If you put a glass of water on a scale and partially submerge an object in it while still holding the object in hand, the scale readout shows an increase in mass. It happens if the density of the ...
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### A body is floating in a liquid of equal density and then pushed down. Why does it sink?

A body is just floating on the surface of a liquid. The density of the body is the same as that of the liquid. The body is slightly pushed down. What will happen to the body? (A) It will slowly come ...
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### Why isnt a taller object more buoyant?

If an objects buoyancy is dependant on the difference in pressure between its two faces, why arent taller objects more buoyant since the pressure difference is larger?
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### Why should Apparent weight of the object floating in a fluid is 0?

The buoyant force act on the object and weight of the body act on water, so do they both cancel out? Now one more thing weight experienced by a body is equal to reaction force acting on a body so here ...
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When deriving the hydrostatic equilibrium for a static fluid, it is said that the net force on a fluid element dV of the fluid must be 0 because it is at rest (on the average, of course). There is a ...
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### How big a vaccum pocket would be required to reduce the weight of an object by one kg?

Let's say we have a very light-weight and strong material ( example ), that could be used to create a vacuum pocket. In Earth's atmosphere, such a pocket would be able to lift weight because of ...
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### Can’t understand the pressure acting on an object when immersed in fluid (Static fluid)

I can’t comprehend two contradictory points regarding the pressure acting on an object immersed in a fluid, as discussed in the Static Fluids section, perhaps because I’m missing on something and I ...
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### A doubt regarding law of floatation

The condition for flotation of a body a little bit above the surface of the liquid is that the upthrust force must be greater than its weight. Why do we in numericals take upthrust equal to the weight ...
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### Floating objects SHM [closed]

I've been trying to look for a derivation of the SHM due to the buoyant force, using proper unit vectors and so on, but to no avail. I've attempted to do it, but after a certain while, I seem to be ...
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### Are normal force and apparent weight the same?

Are normal force and apparent weight the same thing? I'll let ya know the context from which I am asking this question: Is there a normal force on an object submerged in water? So, from what I ...
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### Can buoyant force act downwards? [closed]

I came up with a question stated below "A vessel contains oil (density 0.8g/cc) over mercury (density 13.6g/cc). A homogeneous sphere floats with half its volume immersed in mercury and the other ...
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### Could super-heated gas allow for Dirigibles/Zeppelins/Balloons to go higher than 60 km of altitude?

Well, I don't know much about physics in general, so I hope I don't make too many misconceptions. So, from what I could read in this Wikipedia article, the balloon named "BU60-1" achieved ...
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### Can the apparent weight in a elevator accelerating downwards be compared to that of body submerged in a fluid

Can the apparent weight of a person ( here I mean what a weighing scale would read if that person were to stand on it ) in a elevator going downwards( NOTE: the acceleration is less than the ...
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### Hydrostatics: Glass Floating Up Due to Buoyancy

I'd like to calculate the following problem as a practice for hydrostatics class. There is a glass of height $L$ and diameter $D$ which is turned upside down and then immersed to a depth $H$ in water. ...
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### Could you siphon water from a column of water that is supported by buoyancy?

A cylinder with a radius of $10 \;\mathrm{m}$ and a height of $10 \;\mathrm{m}$ is resting on top of a body of water. The cylinder is less dense than water. At the center of the base (equal to water ...
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### How to calculate the pressure of a trapped, bubble of air 1m below water surface

Ahoy hive mind! The rough scenario I'm looking for some help over is; Picture a tub of $\mathrm{10 \ (l) × 5 \ (w) × 2 \ (h)}$ floating in a body of water The full mass is $50,000 \ \mathrm{kg}$, so ...
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### Would a human be able to descend to depths in the ocean that would crush their body?

Would not the same forces that would crush the body also resist descent? Or would the body be too buoyant to descend below the point at which the water would crush a human?
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### Can a body, made of semi-light material, theoretically float on water (ocean) if it has enough airtight space under it? What are the risks? [closed]

Hello scientists and amateurs, Basically, if I put a quite big airtight container on water and use it as a type of float to wander around ocean (Let's say pretty big, size of a half a football field). ...
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### Bouyancy and Normal force at a fully submerged object [duplicate]

I learned as a child that in a fully submerged object (which is touching the bottom of the fluid tank), the normal force "N" by the tank's bottom to the object is ...
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### What's the shape of a ball held underwater by a flat surface?

I have the following problem: An inflatable beach ball is made of a thin, inelastic, but bendable material. When fully inflated, it has a radius $R$. In an experiment, the ball is filled half full ...
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### Why there is no change to the height of a cube immersed in a fluid when the container is kept in a lift going against gravity?

In a container filled with fluid (say water), and if I keep a cube (having less density than that of fluid) and the height of the cube submerged in fluid be $h$, then if I were to keep the system (the ...
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### Why is the buoyant force of some object equal to the gravitational force of the fluid displaced? [duplicate]

I’ve done the derivation for the buoyant force using the difference in pressures and after everything is said and done the buoyant force of some object in a fluid is equal to the gravitational force F=...
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### How much longer could Titanic have stayed afloat if it gotten rid of its anchor and chain right after hitting the iceberg? [closed]

I am wondering how much longer the RMS Titanic could have stayed afloat if the crew had allowed the ship's anchor and anchor chain to fall to the bottom of the ocean immediately after the ship had hit ...
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### Why is weight in a fluid not equal to the buoyant force?

We know that, weight is the normal force acting on us. And for this 'normal force' to exist 'something' has to be under us. My question is when we're in water on any other fluid, is that fluid that '...
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### A balloon under the ocean

So everybody is familiar with how buoyancy works in theory. However, if I sink a balloon filled with air underwater, the pressure of the water will compress the air inside it, reducing the volume of ...
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### Why does a fluid push upward on a body fully or partially submerged in it?

Now you might think that I'm asking about the buoyant force. And you'd be correct, partially. You see, I understand why the net force on a body submerged in a fluid is upwards. But I want to know: why ...
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### Why this buoyancy machine won’t work? [duplicate]

(Check the video for a better understanding of the machine mechanism: https://www.youtube.com/watch?v=zIdn5zQTJAM&t=109s&ab_channel=RenewjouleLLC ) This machine has a different approach for ...
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### Why generating energy from the gravity side (air column) in a buoyancy chain machine isn’t possible? [duplicate]

(For simplicity let’s say that just 1 ball will be rotating into the machine.) It's proven that in a buoyancy chain machine the needed energy to submerge the ball into the water column will be (...
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### Why doesn't oxygen dissolved in water float to the top?

Shouldn't oxygen form (macroscopic) bubbles and thus float to the top, thus escaping the water? Does the surface tension of water prevent this bubble from popping and releasing the oxygen into the air?...
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### How do you determine if the velocity in momentum is negative or not? [closed]

I am doing a momentum worksheet. Focusing on basic, p = mv and discussing positive and negative momentum. Where "Momentum can be negative if the velocity is negative." .? "How does a ...
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### Boat and Rock Problem: Is there a possible scenario in which the opposite will occur, in that the boat would decrease and the water level rise?

My question concerns the person in a boat with a rock brain teaser. You are in a rowing boat on a lake. A large heavy rock is also in the boat. You heave the rock overboard. It sinks to the bottom of ...
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### Why do individual helium atoms rise?

Balloons full of helium rise because the buoyant force is great than the gravitational force and the buoyant force is due to a pressure difference between the top and bottom of a ballon but why ...
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### Super simple doubt regarding buoyancy/upthrust

Lets keep it short: I am confused regarding the domain over which buoyancy force due to a liquid acts. If I have a hollow sphere and I dip it in water, I observe that it floats partially with certain ...
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### Using the terminal velocity formula for a helium balloon?

I was trying to figure out how to calculate an ascent rate of a helium balloon, and I thought to calculate it's buoyant force $F_b$, subtract it from the gravitational force $mg$, and find some kind ...
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### Why do icebergs flip over?

Why do icebergs flip over? Are certain shapes of icebergs more "stable" than others, in that it's harder to flip them over? If so, why? For example, it somehow makes intuitive sense, that a ...
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### Can spinning increase lift of an air balloon?

If we spin an air balloon, the centrifugal force would cause it to expand, since it is directed outwards. Increased volume of the balloon would increase the buoyant force. Can this be used to ...
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### What is the difference between buoyancy and buoyant force?

We were solving this question, then the instructor mentioned like Buoyancy force is due to pressure difference, what does pressure difference has to do with upward force? Upward force should be the ...
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### Would helium-3 be a better lifting gas than normal helium?

Buoyant force is proportional to the mass of the fluid displaced minus the mass of the volume doing the displacing. Thus the best choices of lifting gas are nothing(vacuum), hydrogen, and then helium ...
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### How would a weightless object behave on earth?

DISCLAIMER: Bear in mind that I am a mere 11th-grader: It came to me that an object with a net zero pounds (on earth) might sit more-or-less statically in the air. An example might be a ball of ...
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### Why don't helium balloons shrink to balance the air pressure?

Helium balloons float because it has less density than air. Why don't the helium gas inside shrink to equalize the air pressure? A quick Google search does not give me any relevant results. (note: I'm ...
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### For a partially submerged object, where is buoyancy force applied to?

Is it applied to center of mass of the entire object, or center of mass of submerged part?
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### Does gravity pull anything up?

I was watching a smoke simulation tutorial (VFX), the trainer mentioned that gravity needs to be turned "on" to have a smoke simulation rise. He mentioned turning gravity "off" the ...
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### How fast does methane rise in atmosphere?

Archimedes' principle states that the upward buoyant force that is exerted on a body immersed in a fluid, whether fully or partially, is equal to the weight of the fluid that the body displaces. If ...
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### Why do we feel weightlessness in water but not on land?

When we draw a Newtonian free body diagram of a man standing still on land, we draw force g and the reaction force. In water when floating still, we still have force g but we also have the reaction ...
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