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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Sensor Temperature with time constant [closed]

I am having trouble with this question on my study guide. I can't seem to find anything on my previous lectures to help me out with it. It is part of my study guide and I think it will be on my exam. ...
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Stratospheric ship

Let's assume that we build a giant steel hull in a shape of cube with open top (2km long edge) and lift it to the top of stratosphere and then pump air out of it. Would it float on the outer layer of ...
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1answer
320 views

Effect of waters changing specific gravity on objects apparent weight placed in liquid

My goal is to monitor the change in specific gravity of a liquid over a period of time. My question is: What are the appropriate formula for determining expected apparent weight of an object immersed ...
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228 views

What is the third law action pair of buoyancy?

Consider a block floating in a fluid. The force due to gravity balances the buoyant force exerted on the block. But there must be a third-law action pair to the buoyant force. If the block exerts a ...
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2answers
58 views

Buoyancy of a positively charged object inside positively charged fluid

An object with a density of $x$ inside a liquid with a density greater than $x$ would float. If we assume that both of these are positively charged and the object is in the middle of the liquid: ...
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1answer
131 views

How to model a rising helium balloon?

I'm trying to model the ascent of a helium filled weather balloon from 0km to 25km altitude. The plan is to eventually use a python script to calculate the time taken to reach 25km. However, I don't ...
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1answer
68 views

Will a rotating body gain linear acceleration in water?

If a ball is floating in water and it has some angular velocity, will it gain some linear acceleration from the drag on it as it rotates? Edit: This is how I pictured it. I guess my reasoning is ...
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96 views

Can I make a cold air trap (thermal equilibrium)

Thermodynamic buoyancy. I have an air intake for combustion air entering into a basement furnace room. During cold weather, the air enters unchecked (no damper on pipe is allowed). I have this 5 ...
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1answer
85 views

Can we make rigid floating helium spheres?

Is there any material that we can make rigid floating helium spheres out of without it collapsing? I have been playing with surface area and volume formulas and with a bit of trial and error have ...
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3answers
462 views

Archimedes' principle for two liquid layers

Problem: I have a cylindrical vessel of height $H$ and radius $R$. There are two liquid layers in the vessel. The first has density $D_1$ and height $h_1$, the second has density $D_2$ and height ...
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1answer
485 views

Newton's second law, gravity and buoyancy [closed]

A body of mass $m$ and volume $V$ is immersed into the sea. The body moves under the action of two forces: gravity and buoyancy (Archimedes). Gravity force has a magnitude $mg$, where $g$ is a ...
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8answers
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Why does a helium filled ballon move forward in a car when the car is accelerating?

I noticed that when I had a helium filled, latex ballon inside of my car, it moved forward in the cabin as I accelerated forward. The faster I accelerated forward, the faster the ballon went from the ...
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1answer
292 views

How to calculate upward force of a container filled with a less dense gas than the surroundings where it is placed?

I'm trying to determine the calculation which would state the upward force of a container where the density inside the container is less then that in which it sits. Does this calculation change with ...
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4answers
1k views

Can air bubbles sink at extreme depths? [duplicate]

I was thinking earlier about air bubbles in water. if you had a bubble of air (say in a balloon) then as you take it down in water the bubble shrinks because of the pressure and because it is ...
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1answer
615 views

What is the buoyant and viscous force acting on a ball in free fall?

I was thinking about a situation were I have a long cylindrical jar with some viscous liquid in it. I also have a spherical ball with me. I drop the ball into the liquid inside the jar with some ...
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3answers
1k views

Buoyancy of compressed air

In the movie Transporter 3 a submerged car is floated to the surface by filling a large bag with air from the tyres. I know that movies are about the worst places to get examples of physics in ...
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1answer
446 views

Plastic bottle floating and sinking

I was doing this experiment: i take a plastic cup, put in a container of water, it floats – then when I put a coin in the water, it sinks and rests at the bottom. So to make the cup sink, i fill it ...
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1answer
316 views

Can the buoyant force on an object be seen as reduction in weight on a scale?

Consider a container with some fluid of density $\rho_l$ and volume $V_l$. This is kept on a measuring device and has weight $\rho_l V_lg$. Now, consider a block of density $\rho_b$ and volume $V_b$. ...
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1answer
1k views

Definition of Buoyancy Flux

I've seen in some papers the definition of buoyancy flux as follows $$B = g \frac{\rho_a-\rho_0}{\rho_0}Q$$ where $g$ is the gravity acceleration, $\rho_a$ is the density of the ambient fluid, ...
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1answer
167 views

Buoyancy in muddy water

Consider the buoyancy force in water with very small but macroscopic particles in it. Such particles (suspension) will very slowly drift downwards and will eventually settle on the bottom. If one did ...
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1answer
130 views

Time to immerse in a fluid

Whenever you drop an object in water, it takes some time to get fully immersed. I was wondering if this depends upon the buoyant force of the water on the object, slowing it down. However, I was not ...
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1answer
101 views

Are the forces I'm using correct? (ball in air) [closed]

I have been working on a program which should simulate all the forces on a spherical object. Right now those are balls, but they can easily be changed to something else. These are the formulas I use ...
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2answers
245 views

Help with buoyant forces and liquids (high school physics)

I am stuck on this problem. Here is the scenario Suppose you send a balloon (filled with air) from your submersible craft to the surface of the ocean, $10.8 \text{ km}$ above, with the ...
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1answer
364 views

Buoyancy Problem - Cubes in water

I have a tank with water (10 m high) , with an ideal seal at the bottom (water can't fall down, but can enter bodies). I have a system of 6 cubes ( of polystyrene density= 20 Kg/m^3) with dimension ...
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2answers
215 views

What is the sensation by man carrying a water bucker with an object floating in it? [closed]

A man is carrying a bucket with water. If a object is kept in it which floats in water, man will feel 1) heavier 2) lighter 3) none I think when the body floats its weight is balanced by upthrust ...
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1answer
128 views

Lifting house with balloons [closed]

I have an assignment about the movie Up. Here is the question: Critique the brief floating scene. Did the animators use enough balloons during this scene? What important variables, (which affect ...
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1answer
3k views

Floating Objects and Weight

The Situation: A ball is placed in a beaker filled with water and floats. It is also attached to the bottom of the beaker via a string. The Question: The ball is attached to the beaker, thus ...
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1answer
121 views

Finding the work required to move an object under pressure without knowing volume

"What is the least amount work you must issue onto a silver ingot with a mass of 38 kg at 26 meters depth to bring it to the surface?" I'm not sure how to do this one. Surely it depends on the volume ...
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1answer
965 views

Application of Archimedes Principle

A candle is floating in a liquid placed in a container. The container is a cylinder of diameter $D$, and the candle is of width $d$. ($D>d$) The height of the liquid from the bottom of the ...
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3answers
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how dense fluid affect the buoyancy force?

I read a story regarding the Archimedes' principle in a magazine of popular science and I am thinking of the following question: how does the density of the fluid change the buoyancy force for the ...
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1answer
412 views

How does the buoyant force on a cube at the bottom of a tank of water manifest itself?

Let's say a 10N cube (in air, on Earth) rests flat on a scale at the bottom of a tank of water, and the scale reads 8N, so there is 2N of buoyant force on the cube. How does the buoyant force ...
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1answer
120 views

Measure density with the help of buoyancy

I am trying to derive a formula to calculate the density of a irregulary shaped object. I can measure the (false) weight of the object in pure air (of known density), and the (false) weight of the ...
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4answers
345 views

Can a balloon be used as an anchor point for a pulley?

For a physics/ engineering contest, I want to use a large balloon as an anchor point for a pulley. This would allow me to raise and drop masses. However, in testing, when I pull on the pulley the ...
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1answer
268 views

When moving something by entrainment in a fluid stream, where does the energy come from?

The particular Something I had in mind here would be air bubbles that are pulled downwards against their buoyancy by a stream of water falling down a shaft. The work required to push those bubbles ...
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1answer
270 views

In a column of rising hot air, is the velocity higher at the top?

Since the movement of the air is induced by buoyancy, i. e. there's a constant force acting on the air, so I would expect the velocity to increase during ascent, much like an object falling down due ...
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3answers
644 views

How do I correctly express the work required to put an object with positive buoyancy down into a certain depth (of water)?

It seems to me that I can express the work required to put an object under water in the same way that I express lifting an object up against gravity. I. e., in both cases I increase the potential ...
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0answers
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How do I calculate the energy balance of a trompe?

I was quite fascinated by the concept of an ancient type of air compressor, called a trompe. It entrains air bubbles into a falling stream of water via the Venturi effect, and extracts the air at a ...
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0answers
61 views

Displacement of a Rock Thrown Overboard [duplicate]

Possible Duplicate: Basic buoyancy question: Man in a boat with a stone If you have a large boulder on a boat, in a pond, and you throw the boulder overboard and into the pond, would the ...
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1answer
171 views

How do I correctly scale down a space capsule for testing its physical behaviour on splashdown?

Kristian von Bengtson (on twitter, on Wikipedia) of Copenhagen Suborbitals is building a downscaled test item to test the design for their space capsule. He notes that as volume and area scale down ...
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3k views

How much lift does the average latex helium filled party balloon produce?

How much lift does the average helium filled party balloon produce? (not including any extras like ribbon string)
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1answer
4k views

Boussinesq approximation for the Navier Stokes' equation - discrepancy

In the Navier Stokes' equation: $\rho_0 \left( \frac{\partial v}{\partial t} + v \cdot \nabla v\right) = -\nabla p + \mu \nabla^2 v + \hat{f}$ I included the temperature variation of density as ...
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3answers
2k views

Cause of buoyant force?

Can you explain to me what causes the buoyant force? Is this a result of a density gradient, or is it like a normal force with solid objects?
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3answers
3k views

Dropping an anchor from a boat

A yacht on a lake drops its anchor overboard. What happens to the water level in the lake? It rises very slightly. It falls very slightly. It stays exactly the same. It's impossible ...
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2answers
696 views

A man on a boat, with something in his hand [duplicate]

Possible Duplicate: Basic buoyancy question: Man in a boat with a stone A man is on a boat, in the middle of a quiet lake. He has something in his hands (anything you like) He throws the ...
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1answer
352 views

Calculate the stable height of a balloon

My son has asked me a question, and I'm afraid my high school maths are not up to the task: Is it possible to calculate the height that a given balloon (filled with a known quantity of helium) will ...
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3answers
893 views

Buoyancy in gases

If buoyancy is caused by pressure gradient and if the pressure of a gas is same everywhere in its container, which means there's no difference of pressures on surfaces of the lighter-than-air object, ...
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2answers
330 views

Infinite Energy from Bobbing

Could this device theoretically continue in motion forever? If not, why not? (click below for images): Device description. Device process. The device is less dense than air, so it rises. The ...
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1answer
104 views

In hydrostatics, is it possible for the bouancy to be greater than the weight of a body?

In the diagram we have two bodies, with density and volume $\delta$ and $V$, and a fluid $\ell$. $$\delta_1=0,7 \rm\frac{gr}{cm^3}$$ $$\delta_2=2 \rm\frac{gr}{cm^3}$$ $$V_1=100 \rm {cm^3}$$ $$V_2=10 ...
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2answers
7k views

Basic buoyancy question: Man in a boat with a stone

This comes from a brain teaser but I'm not sure I can solve it: 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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1answer
95 views

How do we describe the relationship of balloon size and related lift?

We know that hydrogen and helium are lighter that air. Therefore it is certain that they would create a lifting force when enclosed in a balloon. How do we describe the relationship of balloon size ...