# 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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### Buoyancy basics

I was solving this question and in the solution, they have applied a buoyant force exerted by kerosene. It makes sense by the basic definition of the buoyant force from Archimedes principle. However, ...
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### Buoyant force on a stick making an angle theta with the vessel

I was solving this question The answer of the question uses balancing of torques. It uses $L=0.5$m I have problem with the fact that they have used buoyant force $F = \rho V g$. Marking the net ...
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I was reading about boats, from what i was reading a qubic meter of air should be able to float a 1 ton boat so as far as i understand the equalibrium point will be if a boat wight is 1 ton - 1 qubic ...
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### Why the density have anything to do with initiation of subduction?

No matter wherever I read the process of subduction, I always find this one sentence which says "when the two tectonic plates collide the denser plate gets subducted under the lighter plate ...
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### Buoyant force: lead block on top of styrofoam block floating on water, then swap de blocks around

I have a quick question related to the buoyant force. A block of lead is placed on a piece of styrofoam in water. In this case, the water comes up to the top of the styrofoam. If we now turn it over (...
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### An object is connected to the end of a spring and is immersed in water. What are the forces acting on the object? [closed]

The actual question is A copper piece of mass 10g is suspended by a vertical spring. The spring elongates 1 cm over it's natural length to keep the piece in equilibrium. A beaker containing water is ...
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### The reasoning behind the buoyancy force equation [duplicate]

If I drop a block in water, the pressure experienced on the top of the block is the $\rho gh$. That is because a certain amount of water is distributing a force above the block. I don't understand why ...
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### Helium balloons losing buoyancy in cold environment

I recently conducted an experiment in the mountains (approx 1700m above sea level) using a series of large tethered helium balloons to measure windspeed at different heights. After only a few hours, ...
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### If an object is accelerating when it enters water, will the buoyant force change?

If an object is accelerating when it enters water, will the buoyant force equation be changed to $B = V\rho(g + \text{acceleration})$? Or will it remain the same?
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### WIll bucket weigh more?

Let's say I have a bucket filled with some liquid which is not compressible. I also have an object with the same density as this liquid. Since the liquid and object have the same density. Object would ...
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### In which case do the center of buoyancy center of gravity coincide for a body with uniform density. Would it be completely submerged or just immersed

I read other as well in this topic but they dont exactly explain about the body being partially immersed or completely submerged. I mean does the coincidence of centre of buoyancy and centre of ...
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### Buoyant force application [closed]

An open bottle lies on a precise weighing scale. A fly then enters the bottle and flutters around in futile attempt to escape. Another fly, instead of using its wings to fly, uses a small helium ...
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### Velocity of a body after rising out of a ideal liquid

Suppose you have a cube of volume $S m^3$ and you submerge the lower edge of the cube to a height $h$ below the surface of the liquid. $h>S$ i.e the cube is completely submerged. Now, once you ...
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### What will happen if 10kg massed hydrogen ballon is released in air?

Generally, a hydrogen balloon would float when released in air, but what will happen when that hydrogen balloon has a mass of 10kg. Is it the density that decides whether an object floats in air or ...
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### What is definition of weight?

What is definition of weight? Does weight of an object change under water, or the weight remains the same, but the: 'apparent weight' = 'weight' - 'buoyant force' ? Same question for object submerged ...
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1 vote
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### Would a candle in very high gravity blow itself out?

A candle creates an upward draft of hot air, without which the flame would be spherical. The buoyancy generated is proportional to the density difference as well as the strength of gravity. Suppose a ...
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### Adding mass to a bowl until it sinks [closed]

I've been struggling with this question. A hemispherical bowl of inner radius $r$, density $ϕ$ and thickness $t$ is floating in a fluid of density $ρ$. The bowl is being filled with sand at a constant ...
1 vote
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### Confusion regarding a wooden block floating in water in a sealed container [closed]

Consider the following situation: a wooden block floats in water in a sealed container. When the container is at rest, $\frac14^{th}$ of the block is above the water. When the air pressure inside the ...
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### Buoyancy: True mass (2nd law of newton and density ratio) [closed]

How can I calculate the true mass of an object in a fluid (f.e. air)? Given: force measurement (F = 863000 N) air density (rhoA = 1,29 kg/m^3) object density (rhoO = 1100 kg/m^3) g (g = 9,807 m/s^2) ...
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### Does a object, that is partially submerged in a liquid, lose any weight?

I know that all objects, regardless of their density, feel buoyancy force. But do partially submerged, meaning an object that has lesser density than the liquid,lose weight. For example and object ...
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### Could a fish swim out of a sphere of water in a zero-gravity environment?

Can a fish swim out of a sphere of water in a zero-gravity environment? I am going to state some assumptions. We assume the sphere of water is not affected by any thermal properties of its zero-...
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### Experiment about a sphere in a tube in presence of viscous resistance

Recently, I carried out an experiment at home with little equipment, but I can't get to the bottom of it. Consider a fluid-dynamic resistance force of intensity $F_L$ ($\vec F_L = - \alpha \vec V$) ...
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### Conceptual misunderstanding in Buoyant forces [closed]

This is the problem:A piece of ice floats in a vessel with water above which a layer of a lighter oil is poured. How will the level of the interface (oil and water) change after the whole of ice melts?...
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### If an object suspended by a string is immersed in a liquid, will its weight contribute to the pressure at the bottom of the container?

We have a metal sphere completely immersed in a liquid of density A by means of a string. Since the sphere is exerted by the buoyant force due to the liquid the sphere must also exert an equal and ...
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### An ice cube containing a metallic ball in it is floating in a vessel containing water. When the ice melts, what happens to the level of water?

I understand the fact that if there was no metallic ball in it, then when the ice melts, the level of water would neither rise nor fall. Now let us consider the case where there is a metallic ball in ...
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### Is buoyancy affected by container geometry? [duplicate]

Is it possible for something that can't float in a rectangular container to float in a triangular container?
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### Confusion about the "Volume" in Archimedes principle

In Archimedes principle $F_b = \rho gV$. $\rho$ = density of fluid, $V$ = volume displaced by the fluid, and $g$ = gravity. If you have an object in the air, like a balloon, how does the volume work? ...
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### Buoyancy in the hydrostatic equation

I have a question regarding the fundamental equation of hydrostatic, namely: $\vec\nabla P=\rho \vec g$. Why do we not take into account in Newton's 2nd law (used to prove this equation) the buoyancy? ...
1 vote
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### What is the effect of pressure differentials due to gravity on buoyancy force?

First of all, I am aware that this question has been answered in the past, however I have some follow up questions particularly regarded the argument posited in Why is Buoyant Force $V\rho g$? : When ...
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### Could a perpetual motion machine be made using a filling buoyant object that sinks when filled and releases when bottoming out? [duplicate]

Could you make a perpetual motion machine via buoyancy? If you started with 2 types of fluids with different buoyancy. Then add a buoyant object capable of filling with the top fluid where it closes ...
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### How can the weight of a container be affected by an object's buoyancy?

Suppose a table tennis ball is immersed in a fluid and held down by a string. The container is placed on a scales. What will happen to the reading of the scales if the string breaks? How can you ...
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### Was the Michelson & Morely experiment ever valid? [closed]

One of the key predecessors to Einstein's Relativity was another theory having to do with an "Aether" material. This substance was supposed to be the substrate that the universe is built ...
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### Potential energy of a gas lighter than air

Here is the situation. Let's say I have have a mass of a given liquid and I heat it to create a gas. The gas has a lower density than air, so it will move higher and higer in the atmosphere. Then, I ...
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### How much salinity is needed for everyone to float?

Everyone floats in Dead Sea because it is so salty. Is it true in Great Salt Lake? How about Red Sea and Mediterranean Sea? Is it impossible for anyone to sink in these seas without added weight?
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### What is the Buoyant force experienced by a cube at a certain level inside water?

I'm not able to comprehend the meaning of buoyant force. As per Archimedes Principle, it's the force equal to the weight of the volume of water displaced by the body. But wouldn't this be only true ...
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### Does buoyancy force depend on the acceleration of the buoyant object?

According to Archimedes' principle, the buoyancy force on a submerged object is given by the product of the mass of the displace fluid and the gravitational acceleration. Effectively, it is determined ...
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### How does a static fluid exert pressure in upward direction? [duplicate]

I was going through the derivation of a mathematical equation for the upthrust exerted on a body which is given in my book. It says that the downward pressure exerted on the upper surface is less than ...
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### Why are there 2 ways of predicting if an object will float or not?

I thought about it for a second, I have always thought that for an object to float it had to be less dense than water, and if it had more density then it would sink. But then if it sinks or floats ...
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### According to an equation I derived, an object with negligible height would always sink. Where is it flawed?

Assume that an object has negligible height, i.e., height is approximately $0m$. If we immerse this object in water, will it float or sink? In order to find this out, we need to calculate the net ...
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### Buoyancy with Object of Heterogeneous Density [closed]

The Archimedes buoyancy principle usually seems to be taken for objects of homogeneous density. So for example a sphere would have mass equal to $(4/3) \pi r^3 \rho$, where $\rho$ is the density. ...
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### How does the hydrostatic paradox operate when a column of lighter liquid rests atop a “floor” of heavier liquid?

I know that, according to the hydrostatic paradox, the height of a homogeneous liquid is the only determinant of pressure within that homogeneous liquid, and the shape of its container does not affect ...
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### Is the buoyant force on an object a kind of normal force?

So, simple question, are the bouyant force applied to an object by a fluid and normal force (Is it even there?) related? If no where is the normal force and why does bouyancy even happen?
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### Is there a depth under which the buoyant force is no longer sufficient to bring a diver back to the surface? [duplicate]

I came across the story of diver Yuri Lipski who died while diving in the Blue Hole. This made me wonder something and it may be a stupid question but I thought I'd ask: For a human diver with normal ...
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### Sealed container with half-open gas buoy

Consider a sufficiently rigid and sealed container completely filled with liquid (e.g. water), pressurized at 1 bar, at constant temperature. Inside the container there is a buoy partially filled with ...
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### Is it correct to say that "WE" feel only 5/140 of the actual weight of brain as buoyancy acts on brain due to cerebrospinal fluid?

Many sources of biological sciences (e.g.https://medium.com/@drvnx/what-is-that-thing-without-which-we-are-dead-f556fb1029ef ) say that the actual weight of brain is almost 1400gwt but as brain ...
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### How to derive the formula of the buoyant force?

I've seen some variations of this question on the forum, but none has satisfactorily cleared up my confusion, so I made this post with information about what I take issue with specifically. Thank you! ...
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### Buoyancy force vs object weight

If an object is floating (partially or fully), does the buoyancy force = the weight of the entire object? My confusion is, situation A: 100g object is 50% submerged and floating situation B: 100g ...
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### How does inertia affect an object suspended in a fluid?

When I asked my physics teacher how fully submerged objects are suspended in fluids, she told me it was because the object's density was equal to that of the fluid's as a result of the net force ...
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