Buoyancy Definition and 413 Threads

I have a hypothetical scenario I'd like to try understand, and I cannot find anything of the sort online nor in the forums. If I have a balloon of 1 m3 filled with oil, of a density of 850 kg/m3. Now I place this balloon in a body of water and tether it to a fixed point, how can I find the...

Question: Balls A and B of equal mass are floating in a swimming pool, as shown below. Which will produce a greater buoyant force? (Image shows two circles with circle A larger than circle B) A. Ball A B. Ball B C. The forces will be equal D It is impossible to know without knowing the volume...

Homework Statement There is a block of wood floating on the surface of a body of water, with a ball attached to the bottom of the block by a string. I am asked to find the volume of the ball given the tension in the string. We also know the volume of the wood block from an earlier problem if...

Homework Statement A box shaped vessel, of ##4## compartments and ##80m## lenght, light displacement of ##800## tonnes loads ##200## tonnes in the first compartment and ##200## tonnes in the last compartment. Produce the shearing force diagram and bending moment curve. Homework Equations 3...

Dear PF Forum, Our atmosphere consist of 78% N2, 21% O2, 0.9% Argon, and other... https://en.wikipedia.org/wiki/Atmosphere_of_Earth What about theses gases? Will they form a layer like this liquid because of their buoyancy difference? Or they will be scattered evenly because of the wind. I...

jfizzix submitted a new PF Insights post Understanding Buoyancy: The Limits of Archimedes Continue reading the Original PF Insights Post.

When a dense object sinks in water, it sinks at a constant rate, because the buoyancy and fluid drag counteract the weight of the object. But if there is no resultant force, then why does the object slow down when it enters the water? Eg. if it's traveling at 2 m/s when it enters the water...

Situation : A man faces difficulities to pull out a fish from the water when half of the fish body is already out of the water. How would you explain this?

A small solid sphere of mass M0, of radius R0, and of uniform density ρ0 is placed in a large bowl containing water. It floats and the level of the water in the dish is L. Given the information below, determine the possible effects on the water level L, (R-Rises, F-Falls, U-Unchanged), when that...

Homework Statement A bar suspended in air weighs 1.75 N The same bar weigs only 1.4 N when suspended in water. Calculate; a. upthrust b. density of the bar Homework Equations D = m/v F = m*a The Attempt at a Solution a[/B]. Upthrust is 1.75 N - 1.4 N = 0.35 N b. Assuming density of water...

Homework Statement Just trying to find an equation for buoyancy force. Homework Equations The Attempt at a Solution If weight of an object in a fluid density of the object _______________________= ________________ weight of the displaced fluid density of fluid Than weight of object x...

Homework Statement A wooden cube is floating in water. The upper face of the cube meets the surface of a pool of water when a block with mass 0.200 kg is placed on top of the cube. When you remove the block, there's a 2 cm difference in height between the upper face and the water surface...

I am working on a project in which I must move an object a moderate distance (left to personal preference) using buoyancy as the main mechanism of movement. I have a few ideas for how to accomplish this, but I am having major problems thinking about how to implement aspects of each. Below I...

I've never been able to figure this out. I can understand when you put oil in water that one floats on top of the other, but why does it still work if I put it into a balloon? Something that keeps it from directly interacting with the medium it's in?

The usual form for tension as a result of the symmetric Cauchy stress tensor is, $$\mathbf{t} = P \mathbf{\hat{n}}$$ or better $$t_i = {P_i}^j n_j$$ Buoyancy would be $$T = \int_{\partial V}{P_i}^j n_j da$$ integrated over a closed surface. I've assumed that the stress tensor ##P##, is, in...

Finding the landspeed a object needs correlating with its area and weight in volume that a object needs to stay above water looking for the equation and plug in methods

Homework Statement If an object is 500 N normally but has an apparent weight of 300 N when submerged in water, what is the density of the object? Homework Equations ρobjVobjg = ρfluidVobjg The Attempt at a Solution So the correct answer is 2500 kg/m3 but when I set up the problem, it doesn't...

I am trying to design the housing for an electrical core so that it remains buoyant on the surface but can be neutrally buoyant at desired depths through ballast tanks. I am trying to figure out what the core and housing may typically weigh through specifications online of ones already made...

Hello, the known presenter "Vsauce" on youtube had a video in which he talked about a " space straw" basically a pipe or circular enclousure the goes from a higher pressure area to a much lower one like a straw from surface of water at sea to outer space. Now , my question is If I were to put...

A question about PSI and buoyancy. How does the air pressure of a container effect whether the container will sink or float? For instance, if two containers of the same mass and area (and the mass of the container itself is negligible), one container is filled with 10psi of air and the other...

Homework Statement An iron casting weighs 300 N in air and 200 N in water. What is the volume of cavities in the casting, if the density of iron is 7800 kg/m3 ? Homework Equations d = m/V Fg = mg The Attempt at a Solution I was not sure in the slightest of how to solve this problem. So I...

I need to know approximately what percentage of a vehicle with an airtight passenger compartment must be filled with water before it sinks to the bottom. The fact that it is airtight may normally prevent it from sinking, but if a window was cracked from impact, and water slowly trickled in...

Homework Statement What diameter must a helium filled balloon have to float with neutral buoyancy? The mass of the empty balloon is 2 g. Homework Equations FB = (density)(gravity)(Volume) Volume of balloon = 4/3(4.13)r^2 Density = mass/Volume The Attempt at a Solution I know that the...

A flask of water rests on a scale that reads100 N. Then, a small block of unknown material is held completely submerged in the water. The block does not touch any part of the flask, and the person holding the block will not tell you whether the block is being pulled up (keeping it from falling...

Homework Statement A small solid sphere of mass M0, of radius R0, and of uniform density ρ0 is placed in a large bowl containing water. It floats and the level of the water in the dish is L. Given the information below, determine the possible effects on the water level L, (R-Rises, F-Falls...

Homework Statement A cube of ice is floating in water such that some part of the ice is submerged. Oil is poured on the water.( so water on the bottom, oil on top and ice in between). When the ice melts completely, the level of oil-water interface ______(rises/falls) and the top level of oil...

My question is when a boat is floating on top of the water is the weight of water that is being displaced greater than the weight of the entire boat, or just the portion that is submerged?

I am fifteen and I attend High Tech High International and I have to teach a hour long lesson on Black Hole Buoyancy. And I was wondering how to do that. Can I have some suggestions or help?

Homework Statement A solid is completely immersed in a liquid. The force exerted by the liquid on the solid will(more than one right) (a)increase if it is pushed deeper inside the liquid. (b)change if its orientation is changed (c)decrease if it is taken partially out of the liquid (d)be in the...

In Hooke's law, F=-kx. Assume that a mass is hung from the end of an ideal massless spring, the spring stretches a distance of x. However, in real life the spring has mass and it is submerged in a "fluid" of air. Compared to an ideal spring, would the real spring have a slightly different...

Brief Summary of Question: One submarine starts with a neutral buoyancy 100m below the surface when it displaces 8.9m^3 of water from its ballast tanks. If the mass of the submarine is 69 metric tons what is the initial, vertical acceleration of the submarine immediately after displacing the...

Homework Statement A helium balloon is used to lift a load of101N. The weight of the envelope of the balloon is46.5N and the volume of the helium when the balloon is fully inflated is31.5m3. The temperature of the air is 0°C and the atmospheric pressure is 1.00 atm. The balloon is inflated with...

Homework Statement Block A in the figure hangs from a spring balance D and is submerged in a liquid C contained in a beaker B. The weight of beaker is 1 kg, and the weight of the liquid is 1.5kg. The balance D reads 2.5 kg and balance E reads 7.5 kg. The volume of the block is 0.003 m^3. What...

Homework Statement A piece of aluminum is completely covered with a gold shell to form an object of weight W. When you suspend the object from a spring balance and submerge it in water, the balance...

I have a little confusion regarding bouyancy. Suppose two objects fully immersed in liquid having equal volumes, one close to surface but other at greater depth. As both displace equal volumes of water therefore they should be facing equal bouyant forces. But as the object which is at greater...

Homework Statement A small boat weighing 1000 N has a surface area of 3 m^2. It floats only 5 cm above the water level when in a fresh-water lake. How high out of the water will it ride in a salt-water lake? Assume the surface area of the boat does not change as it rises (salt water has a...

Problem: http://i.imgur.com/o8Q1RGZ.png Solution: http://i.imgur.com/IYiXITJ.png To get d2y/dt2+ρgLby/M=0, you have to sum the forces and set them equal to Ma. But what happens to Mg when you sum the forces?

Homework Statement This problem pertains to the drinking straw trick. You decide to place your finger over a 20.0cm straw. 95.0% of the straw is filled with water, while the top is full of air. Treating the straw as an ideal gas, compute fraction of the straw that is filled with water when the...

I recently posted a question about solids that led to a very productive discussion about solids, weight, gravity and pressure. I learned that many intuitive ideas I had about these concepts were wrong and I now have a better understanding as a result. However, in the course of my reading I came...

Homework Statement 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 coin (see the diagram below). What will happen if I throw that coin inside the...

Homework Statement Question: What minimum volume must a slab of ice in a freshwater lake have for a 50.0kg woman to be able to stand on it without getting her feet wet? Homework Equations Archimedes principle...

Homework Statement When an object is submersed in a liquid, it experiences a buoyant force equal to the weight of the liquid displaced by the object. As an object moves through a liquid, there is a resistive force which is directly proportional to the density of the liquid, the cross sectional...

Homework Statement A rock is suspended by a light string. When the rock is in air, the tension in the string is 35.7N . When the rock is totally immersed in water, the tension is 25.9N . When the rock is totally immersed in an unknown liquid, the tension is 19.6N . Homework Equations Density =...

Hello everyone, I am thinking of a thought experiment about a so-called "space tower" but don't have enough information to estimate the numbers. I understand the material strength needed for such high structures is huge, because of the weight of the structure. But what if the "tower" would be...

Hi there. The energy used for hydrogen production can be recovered using the buoyancy force of the gas created at sufficient depth of water. Suppose we use electricity to split ocean water to produce hydrogen. Then the produced gas is captured into containers which are attached to a conveyer...

This was an extra question in an exam I took today. The temperature of the air in the bottle remains constant. I know this has something to do with buoyancy and ideal gases since temperature was mentioned in the question, and I think I could have easily solved the question, had the submerged...

Hi guys, I have been wrecking my brains thinking bout this for quite some time, so I decided to get some help here :D . Please check the diagram in the link below: http://9gag.com/gag/abq50dE#comment Ok so, can someone explains what happens to the beaker on the left? Would it get lighter as a...

Why is the weight of the liquid displaced = buoyancy force and not the weight of the submerged volume of the object? Does it have something to do with normal force of the surface of the liquid on the object or pressure?

Hello everyone, I am beginner to comsol physics.I am trying to simulate a task which contains implemented lift force of water on a solid structure(nickel). I need to know where to start from? Which modules should i use and which steps should i take? I looked up an example from comsol...

A object B is place on top object B and the object B is fully submerged in the water. So is the bouyance force equal the force apply by object A on object B? Please help.