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 relation between hydrodynamic drag and buoancy force?

Is hydrodynamic drag just the overarching study of liquids in fluid whilst buoyancy force is the upwards force acting on the object? I really do not know much about this topic.
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Derivation of Archimedes principle for a sphere

I am trying to derivate the Archimedes principle for a sphere with direct hydrostatic pressure calculation. I started with the asumptions that: $F_b=F_2-F_1$ and $F_2=2F_1$, where $F_b$ is a buoyancy ...
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This clever device moves heavy rocks upwards against gravity using buoyancy. Where is 'the work' coming from to move the rocks upwards?

So I saw this machine whilst researching the pyramids, and I've become completely fascinated by it. It seems to beautifully demonstrate many of the conundrums of work done, but remains alluring enough ...
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How to calculate the change in angle due to the righting moment of a ship?

I trying to calculate how the forces on a boat (initially out of equilibrium) work to right it. The cross section of the boat is a convex polygon and constant throughout its length. I can find the ...
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193 views

Should this object float?

I was learning buoyancy on Khan Academy and it was going well until I thought of this thought experiment. Consider if you had a tube of water with a hockey puck that completely touches the sides (but ...
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Water level in a sinking boat is constant?

I came across this question in a physics worksheet: "A small hole is punched into the bottom of a rectangular boat, allowing water to enter the boat. As the boat sinks into the water, which of ...
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3answers
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Got confused about weight loss in liquid [closed]

Suppose two objects of the same mass but of different densities are dropped on water. The large object (say polypropylene) has a lower density than water and the small one (say stainless steel) has a ...
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32 views

What is the direction of the force of buoyancy at the bottom of the liquid? [duplicate]

I know that the force of Buoyancy always acts upwards, still I had a doubt Let's assume (everything is ideal), we have a block which is submerged in a liquid which has less density than the block, Now ...
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48 views

What affects Buoyant force?

Why isn't buoyancy affected by the object immersed in water? I know that more depth means more pressure means more buoyancy. But based on Newton 3rd law, the water should apply a force back on the ...
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Direction of forces when calculating net force with buoyancy [closed]

Given an object attach to spring scales showing the mass of the objest is 0.324KG. We then dip the object in the water and the scales shows ...
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Submarine buoyancy

Maybe a silly question but.. A submarine has ballast tanks to control it's buoyancy. To submerge, water is allowed to fill the ballast tanks which displaces the air inside. When a submarine is ...
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What density of an object of more than one substance affects the buoyant force?

If we immerse a sealed cup of a liquid in a fluid, what density is taken in consideration when it comes to the buoyant force, the density of the cup itself (the substance in contact with the fluid) or ...
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Is there a limit to the height to which a helium balloon can rise?

My professor's answer to this is "It will rise until the weight of air displaced equals the mass of the balloon". I am a bit confused by this. Wouldn't it depend on densities rather than ...
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Intuitive explanation of Archimedes' principle? [duplicate]

https://en.wikipedia.org/wiki/Archimedes%27_principle The wikipedia entry for Archimedes' principle (buoyant force = weight of fluid displaced) has interesting formulas explaining why it's true, but ...
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Theoretical justification of buoyancy in two or more liquid layer

If an object is dissolved in a container of two liquid layers so that volume $V_1$ is in liquid 1 and volume $V_2$ is in liquid 2. $ρ_1>ρ_2$ be given where it refers to respective densities. I ...
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Tip of the Iceberg [closed]

Is it possible to approximate the volume of an entire iceberg if one happens to know the volume of the visible tip? (Assume the water is perfectly still.) If so, how may that be done?
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Plausibility of underwater planes [closed]

Wood floats on water because its density is lower than water. A ship made of steel floats on water because the ship is hollow, the overall density of the ship is lower than water. Now if you seal the ...
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Is there a reason behind why Archimedes principle works? [duplicate]

I think most of us are quite aware of Archimedes principle, but is there a reason to why it occurs? Is it just an observed property? Why is the upthrust equal to the weight of the liquid?
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What explains that volume of body submerged is indirectly proportional to the density of liquid? [closed]

I want to have a mathematical proof that explains why the volume of body submerged is indirectly proportional to the density of liquid it's submerged in. As a common example a ship sinks more in river ...
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Weight of liquid with something swimming on it [duplicate]

I was wondering about the following situation: If you'd weigh a whole body of liquid and then let something float on it, how would the weight of the liquid change? E.g. if you could weigh a whole lake ...
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What force does a floating object exert on the liquid it is floating on?

When something floats, it is due to the buoyant force from the liquid onto the object, but what force does the object exert in response down on the liquid? I feel as if the object would have to exert ...
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Since the pressure's greater on the bottom of you than the top, shouldn't there be a force acting upward on you?

Suppose there's an upright cylinder in the water. The pressure at the bottom's more then the pressure at the top, so shouldn't there be a net force upwards? Does this matter much?
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Mass, density, and forces on a floating ball [closed]

If I have two balls, one completely in the water (mass = 4m), and the other half submerged (mass = m), the volume of both balls is V = 15 cm^3. They are tied together with a string. How can I ...
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What is the origin of buoyant force exerted by fluids?

How does the buoyant force come into action all of a sudden when an object is immersed in a fluid?
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95 views

Can the formula of buoyancy be used in this arrangement?

The buoyant force exerted by an object in water is given by $\rho.g.v_{submerged}$ Which only depends on the volume submerged and nothing else(I think) But can it be applied to partially submerged ...
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Does my work suggest that the buoyancy force isn't generally just the pressure exerted on a body? [closed]

If I got it right, the buoyancy force is a result of pressure changes exerted by the gravitational force. Archimedes’ law then generally predicts the buoyant force to be $\rho_\text{fluid} Vg$. What I ...
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Can helium gas lift the bottle itself?

I came up with this argument: it’s possible that in the right circumstance helium would weigh more than the empty bottle. If I were to fill empty bottle full of helium can it lift the bottle in the ...
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Energy budget in a buoyant flow

A cavity, subject to gravity, is filled with a fluid initially at uniform temperature. Initially all boundaries are adiabatic surfaces; at time $t=0$ two opposite boundaries (shown in red and blue) ...
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2answers
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Does the visible part of an iceberg depend on size?

Most people heard that we only see some % of an iceberg above water (10% etc). I suspect the exact % depends on the iceberg's shape (e.g. flat disc vs very narrow cylinder). But, assuming a similar, ...
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1answer
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How to control pitch rotation of an object that is suspended on water

I am thinking about designing an underwater vehicle. It's shape will be cylindrical(12cmx70cm). It will have a pump to pump water into a tank for adjusting density of the vehicle. In that way It will ...
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Line of action of buoyant force [closed]

Question: Show that the line of action of the buoyancy force on an arbitrarily shaped body submerged in a liquid passes through its center of mass My observation: I know that buoyant force is equal to ...
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3answers
129 views

Is buoyant force self-adjusting?

Assume that density of the body is less than the fluid. If we put a body in a given fluid the buoyant force equalise the weight of the body. If we increase weight, the buoyant force increase? If it ...
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Can you explain the meaning of buoyancy, written here?

I got this Archimedes' principles from a website named smithplanets.com Can you explain why we cut the volume of water equivalent to the weight of an object when the object is floating in the water ...
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How do buoyancy and pseudo forces combine?

About the diagram: A tennis ball is attached to a string which is attached to the jar. The string is mass less. The density of the ball is less than that of water. The F.B.D of the tennis ball: Thus ...
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1answer
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Why the inner core of planet Earth is not composed of the densest materials?

I read on various sources the inner core of our planet is said to be mostly composed of a iron-nickel alloy, plus some lighter elements like silicon. On the other hand, I know that in general lighter ...
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Why does a floating object displace more substance than a sunk object? [duplicate]

Consider a box floating on water having a coin on top, now suppose after some time by some external influence, the coin is dropped into water. After doing the calculations, to my surprise, I found ...
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1answer
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How much buoyant force to pull a plastic cube from under a tank of water in to the water?

I'm having a hard time to understand how many same size black cubes would be in order to pull up the bottom black cube in to the water. I know water level is important but I believe there must be a ...
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Will a plastic feel less heavy when I put it in a bucket of water and carry it?

If I'm carrying a bucket of water in one hand and a piece of plastic in the other, and then I decide to keep the plastic in the bucket of water (it floats). Will it feel less heavy in the second case? ...
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Why not to multiply with $g$ when doing sums in the unit $\rm kgf$? [closed]

My book told me a thing to keep in mind while doing upthrust sums in $\rm kgf$. It's stated as follows: (See point number 2) Can you please explain why not to multiply with $g$? Also I am giving ...
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176 views

Temperature effect of rising helium balloon in air

I wanna consider some cases and make sure if im right , if i have fixed volume balloon filled with helium , and let balloon fly in air , 1) if air temperature increases , ( without increasing temp of ...
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1answer
51 views

how to calculate how high would a helium balloon with weight go? [closed]

I knew that one liter of helium would lift approximately 1 gram of mass. However, I could not find how to calculate how high would that 1 gram go. Imagine if we have a helium balloon (ignore the ...
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Fluid Mechanics - Bubbles

Why do gas bubbles initially stick to the walls of the bottle in carbonated drinks? And what happens when we open the cap? How do they separate from the walls?
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Is there any formula showing the relationship between $V$, $A$ and $G$ as mentioned below?

We all know that if we fill a cylinder with water and then drop the egg into the water it sinks but when we add some three tsp of salt the egg floats. Let, $V=$ volume of the cylinder. $A=$ Volume of ...
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Buoyancy - Droplet of Oil in Water

If I place a droplet of oil, which is less dense than water, at the bottom of a glass of water, it should start to rise in the water due to the buoyant force. Will the oil droplet start rising faster ...
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How to infer about the volume of the body from measuring the mass of the object in 2 different liquids?

While solving a problem on hydro statics subject I saw a statement that argued that if I know the weight of the object in the air and then I know the weight of the object in the water.so when I ...
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1answer
257 views

Calculating work done by buoyant force [closed]

Consider a block of size $h\times h\times h$.(Base area=$A$=$h^2$, density=$\rho$). It is kept with half it's height submerged in a tank that is filled with a liquid (density=$2\rho$ with base area= $...
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How to make the weight float on water? [closed]

The height of the cylinder is $3 \text { m }$ and the diameter is $45 \text { cm }$. The cylinder is filled with water. The block is of weight $30\ \text { kg }$ with dimensions $30\text { cm} \times \...
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195 views

How does atmospheric pressure affect the buoyancy of a small particle?

If I have a single cell (phytoplankton) or a small piece of sediment in a lake that is neutrally buoyant, how can I calculate the change in buoyancy due to changes in barometric pressure? For example, ...
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How to calculate the elapsed time while reaching the limit speed?

(Figure drawings belong to me.) In the figure, a person falls freely from the tower at a height of $1500\ m$. When the limit reaches speed, it opens its parachute. By the way, how do we calculate the ...
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Buoyancy perpetual motion machine with compressors at top and decompress-or at bottom [closed]

a link to consideration about the perpetual motion machine [] diagrams and working out are included above. the assumptions are set to minimise engineering challenge and face perpetual motion machine ...

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