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 will happen to a ball suspended in a liquid if we create air bubbles underneath it?

Suppose we have a cylinder half filled with water and a ping-pong ball, floating on the surface. We cut small holes in the bottom of the cylinder and proceed to blow air through it, resulting in air ...
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44 views

What is the motion of a balloon with a person climbing on a ladder?

Suppose you had a balloon of mass $M$ in the atmosphere at rest relative to the ground, with a ladder attached reaching towards the ground. A person (of mass less than $M$) begins climbing up the ...
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43 views

Fluids and pseudo force [closed]

A bucket of water contains a wooden block floating in water with (4/5)th of its volume sub merged in the water. The bucket is placed on the floor of a lift and the lift now starts moving down with ...
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3answers
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What should density of water be to keep box afloat?

I'm writing a platformer game and my physics engine is Box2D. I have successfully implemented buoyancy, but have a question about mass and density. My player is 80kg, a box has a density of 0.5 and ...
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Would a solid inside of a parcel moving due to buoyancy be affected by Bernoulli's Principle?

If a parcel (or column) of hot air were rising due to buoyancy and an extremely light solid were to be inside of this parcel (rising with it), would Bernoulli's effect cause the solid to stay inside ...
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What is the basic reason behind buoyancy?

Yesterday my friends and I were solving this easy-looking question: A metal cube is placed in an empty vessel. When water is filled in the vessel so that the cube is completely immersed in the ...
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Doesn't a box holding a vacuum weigh the same as a box full of air?

This was recently brought up, and I haven't been able to conclude a solid answer. Let's say we have two identical boxes (A and ...
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34 views

Floating objects and fluid statics

If an object is floating, I know about how buoyancy force (density of liquid* volume displaced* g) must equal gravitational force (density of object* volume of object* g). Can someone explain if it is ...
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35 views

Buoyant Force Issue

I don't understand why the buoyant force is equal to the weight of the displaced water for objects that are not "spheres of fluid." Why does the reasoning for fluid spheres hold for other objects?
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How would filling a milk canister with helium affect the reading it makes on a scale?

Let's say that if I put a milk canister on a scale it shows 10kg. If I fill it with Helium it must necessarily be less than this, right? Can someone explain this (probably trivial) thing to me? :) ...
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Metallic coin over wooden block in glass of water

So there is some water inside a container; the height of water inside the container is $l$. I placed a wooden block on the water and it's floating to some height $x$, on top of the block is a metallic ...
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2answers
104 views

Could one make steel balloons? [duplicate]

Reading this question reminded me of an idea I once had, and I wonder whether it's feasible. Imagine a hollow ball made of something strong, like steel. Imagine there is nothing inside; only vacuum. ...
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Force if a diver is lifting a pillar out of the water?(High school physics) [closed]

A diver is searching through the remains of an old shipwreck at a depth of 45 m below the surface of the ocean. The diver finds a marble pillar that is approximately 1.7 m x 0.15 m x 0.15 m in ...
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40 views

Buoyancy Dilemma

Can you give me an example where an object (less dense than liquid) is floating in liquid and buoyancy acting on that object is more than the weight of that object ? It is impossible , isn't it? ...
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2answers
71 views

Is it a misconception? [closed]

In our textbook it is said that if buoyant force is W and weight of an object is w then object will float when W > w object will be submerged and it wont float(it will sink) when W ...
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2answers
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Why won't a block less dense than water fully submerge?

Suppose we have an object of volume $1\: \mathrm{m^3}$. Mass of that object is $500\: \mathrm{kg}$, which means that the density of the object is $500\: \mathrm{kg/m^3}$. If the object is in water it ...
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1answer
50 views

Bouyant force in air on hollow object

I understand that the buoyant force is equal to the weight of the air displaced by the volume of the object. I also know that if we had a perfectly solid cube or a hollow cube closed on all sides so ...
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Reaction force for buoyancy?

According to Newton's 3rd law each force (action) has a counter-force (reaction). What is the reaction (counter-force) of buoyancy?
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The physics behind Balloons lifting objects?

Apologies for the super basic question, but we all have to start somewhere right? Can somebody please explain exactly how you would calculate the number of helium balloons it would take to lift an ...
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2answers
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Why do Oreo crumbs float to a single glob at the very center in a glass of milk? [duplicate]

I had Oreos and milk a while ago and left my half-full cup of milk out on the counter. Afterwards I noticed that the crumbs had surfaced in a circular coin-sized glob, and just now I looked again to ...
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Why doesn't a tied balloon behave like a pendulum?

It is well known that a tied weight will oscilate under the effect of gravity if left from aside, like a pendulum. However, if we tie a helium balloon to the ground from and left it form the floor ...
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1answer
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If hot air expands in all directions why is the balloon moving up?

A balloon is moving up. The hot air inside the balloon is expanding in all directions and cold air outside the balloon acts with force on the balloon from all directions (higher pressure force). Why ...
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1answer
73 views

Buoyancy / Drag Problem

Buoyancy / Drag Problem Just a little bit of help would be nice. I have a spherical particle of radius $R$ and density $\rho$, surrounded in a fluid of density $\phi$ and viscosity $\eta$. I'm ...
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Why is Buoyant Force $V\rho g$?

For a submerged object, buoyant force ($F_b$) is defined as: $$F_b = V_{\text{submerged}} \times \rho \text{ (density)} \times g \text{ (gravitational constant)}$$ Conceptually, the buoyant force ...
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158 views

How to calculate the buoyant force on a balloon at different altitudes [duplicate]

For a project into balloon simulation I'd like to know how the force on a balloon changes with altitude: I know that the Buoyant force on a balloon is: $F = (\rho_{air} - \rho_{helium})gV$ Using ...
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Pressure and Buoyancy [closed]

It is well known that you can trap water in a drinking straw by placing the tip of your finger over the top while the straw is in the water, and then lifting it out. The inner diameter of the straw is ...
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Definition of buoyancy

Hi I'm trying to figure out the definition of buoyancy, is this correct? So say for example I have 1 cubic meter of water which weighs 1 ton, and I placed a cubic foot of a material that at a 1 ton ...
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1answer
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The Spinning Log “Perpetual Motion” problem, and my attempt at a solution

So I was introduced to this "perpetual motion" riddle a few weeks ago. The problem goes like this: we all know perpetual motion machines are not possible, but this riddle seems like it should work as ...
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3answers
326 views

Finding the density of gold crown using archimedes principle [closed]

Question: As shown in diagram below the crown has a mass of 14.7kg when measured above water and 13.4kg when measured in water. Is the crown made of gold? I have this following solution provided: ...
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Which way does the scale tip?

I found the problem described in the attached picture on the internet. In the comment sections there were two opposing solutions. So it made me wonder which of those would be the actual solution. So ...
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1answer
145 views

When you breath in a helium balloon, do you lose weight?

We all know the trick of breathing in a helium balloon to get a funny squeaky voice! When you do this, would it be correct to say you lose weight? On the one hand, the helium should make you more ...
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Flying eggshells

This question was asked on Judaism.StackExchange a few days ago, but I think it has a better chance of being answered here. Disregarding the grammatical discussion in the comments on that ...
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1answer
248 views

Calculate the weight that a hot air balloon can carry [closed]

Given a hot air balloon of radius 10 meters and negligible mass, calculate the maximum weight it can carry if the density of outside air is 1.2 $\frac{kg}{m^3}$ and the density of inside air is 0.9 ...
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4answers
154 views

How does buoyancy work?

I realised, reading another Phys.SE question about balloons moving forwards in an accelerating car that I don't really understand how buoyancy works. Particularly concerning, for a SCUBA diver. The ...
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4answers
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Basic buoyancy question

If I have a cup of water filled with air at the bottom of a pool, then when the cup is "upside down" the air doesn't leave because the water pressure is pushing it up against the top of the container. ...
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1answer
134 views

Terminal Velocity of buoyant object

I'm trying to figure out how much distance does a ball of balsa wood covers until reaching terminal velocity, being released from a bottom of a pool. To my understanding, I need to first figure out ...
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65 views

How does one calculate calculate buoyancy with gases?

I have hot air flowing vertically down a circular duct into the ambient cold air. I'm trying to find the power $P$ that resists the flow. I know the: Volumetric flow rate $Q$ $[m^3/s]$ Flow speed ...
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344 views

water surface tension and buoyancy

When you put a little pin on the surface of water and it floats. Is this because of surface tension or buoyancy? Can somebody also draw a force diagram for me to explain how water surface tension ...
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Archimedes' principle: innacurate terminology? [duplicate]

All around I read that buoyancy is numerically equal to the weight of fluid displaced by a submerged object, the volume of displaced fluid being equal to that of the submerged portion (Wikipedia). ...
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Balloon, lighter than air and vacuum?

As I understand, in a balloon/air balloon, a gas burner is used to heat air or using some lighter atom like helium. Since helium or hot air is lighter and less dense than the cool air around the ...
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218 views

Upthrust vs Drag

24: A ball is falling at terminal speed in still air. The forces acting on it are upthrust, viscous drag and weight. What is the order of increasing magnitude of these 3 forces? ...
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62 views

I need to find a formula between the weight of an object and the volume of the buoy that can float it on water

So my problem is that i am working on an art instalation that needs to float. The idea is that i need to find a formula between the volume (V) of the buoy and the total weight of the whole ...
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Why does ice melting not change the water level in a container?

I have read the explanation for this in several textbooks, but I am struggling to understand it via Archimedes' principle. If someone can clarify with a diagram or something so I can understand or a ...
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2answers
127 views

Can a solid object float on a frictionless liquid?

Assuming the solid is less dense than the liquid, will a solid object float on a frictionless liquid? I can imagine that due to the pressure gradient the object will float, but I can also imagine ...
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Anchor of a boat

hope you can help I've been teaching my kids about pirates and when we were talking about pirate ships this morning I confused myself greatly. When carrying an anchor a pirate ship (or any vessel ...
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3answers
371 views

Does gravity cause Archimedes' principle and how?

Why do lighter objects float and denser sink? I understand this from the perspective that if the object can displace the equal mass of water it will float, but I wonder from the perspective of ...
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2answers
164 views

If the MH370 black box did sink to 15000 ft, how long would it have taken?

I have been following MH370 on the news just as everyone and latest reports seem to indicate that the black-box could be found. A recent info-graphic http://t.co/lyBBE9C2hF shows the insurmountable ...
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179 views

Question about buoyancy

I took an empty clear sphere with radius r, put some weight inside this sphere, and put in into the water. I calculate the buoyancy force as: Volume of the sphere = Volume of the water displaced ...
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1answer
115 views

Different solutions for floating a DIY torii gate deeper than it's original floating level [closed]

I'm facing a dead end with my physics experience on a new build I am working on. Any help would be appreciated. Basic problem: I am trying to build a floating wooden Torii gate to be placed on water ...
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2answers
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Beryllium Vacuum Sphere Boat/Aircraft

Is it possible to make a solid rigid evacuated "balloon" out of Beryllium or other elements or alloys? The critical buckling pressure at which an evacuated sphere is given as $$ ...