# What is Archimedes principle: Definition and 106 Discussions

Archimedes' principle states that the upward buoyant force that is exerted on a body immersed in a fluid, whether fully or partially, is equal to the weight of the fluid that the body displaces. Archimedes' principle is a law of physics fundamental to fluid mechanics. It was formulated by Archimedes of Syracuse.

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1. ### Calculate the bouyancy of two spheres joined by a rope submerged in seawater

m * g = mAl * g V * ρ * g = VAl * ρAl * g V * ρ * g = V * ρAl * g ρ = ρAl this does not work at all, because the upper ball must have a density smaller than that of seawater 1200kg/m3 or not?
2. ### B Archimedes Principle - A Rock and Water Magic Trick

I understand how to measure specific gravity of a rock. One weighs the rock then tares a beaker of water and then suspends the rock on a string to observe the “weight” gain of displaced water. My brain however could never get how, without adding a drop more water or adding the mass of the rock...
3. ### Dropping anchor from the barge

(I must confess before I can begin that I found this problem difficult to understand, for reasons I will make clear below. I know it appears simple.) Attempt : Let me begin by drawing the problem situation alongside, to the best I understand. We can see that the in both cases (i) or (ii), the...
4. ### MHB Physics - Archimedes principle

Im having trouble with the following question regarding Archimedes principle. A wooden board with an area of 4.55m^2 is dropped into the dead sea (P sea- 1240 kg/m^-3). Calculate the proportion that would float above the surface. (P wood - 812 kg/m^-3). My understanding is that the volume (V...
5. ### Sinking a toy boat with lead pellets

Attempt : I begin by plotting the graph of depth x against mass of pellets m as shown alongside. Using ##m_B = \Delta m_L\Rightarrow m_B = \rho_L A_B\, x(B)## where ##\rho_L## is the density of the liquid, ##A_B## is the cross-sectional area of the boat and ##x(B)## is the depth to which the...
6. ### Atmospheric pressure as a function of altitude

Summary:: i) Set up a differential equation that describes how the pressure ##p## varies with the distance r from the center of the planet. Hint: You can base your reasoning on static equilibrium and Archimedes' principle. ii)Calculate how the atmospheric pressure p and the density of the...
7. ### B How does the weight on a scale change when an object is submerged in water?

Dear, I am a medical doctor and my physics background is limited to that of secondary school many years ago, but should want to ask for your help. In attachment, you can find a picture of my question. On a scale, we place a jar filled with water. We place in the water a platform which is...
8. ### Hollow and solid spheres floating in liquid

The two situations are shown in the figures alongside. The hollow sphere has a thick heavy rim that compensates for the air inside it - both spheres have the same mass ##m_B## and radius ##r_B##. Since the bodies have the same mass ##m_B##, the mass of liquid displaced is the same ...
9. ### Engineering Using the Archimedes Principle to do calculations for this floating buoy

A Spherical buoy has a diameter of 2m and weighs 3kN. It is designed to be used in a variety or circumstances by it being floated in water and anchored to the floor with a chain. Draw the free body diagram and determine the following given that the volume of a sphere is, Volume = πD3/6 The...
10. ### Question about calculating the minimum temperature in hot air balloons

First, I tried using the Archimedes principle and calculated the weight of the surrounding air displaced when taking off. ##W = 2500\times 1.29\times 9.81 = 31637.25 N## But then, I got stuck and do not know how to proceed from here on. I don't want the full solution yet but can I get some...
11. ### Comparing densities of three bodies floating to different depths

The dimensions of the bodies given in the problem are visual. Clearly bodies a and b are cubical whereas c is not. One side of b is twice the side of a. Both a and b are submerged to the same depth but what is the depth of submersion of c? Arranging bodies (by copying and pasting a on b and c...
12. ### Buoyancy and the Archimedes Principle

Hello all I was hoping someone could help me with some intuition regarding Buoyancy and Archimedes Principle. I thought i understood Buoyancy in terms of pressure but when i came across Archimedes Principle I realized I did not fully understand what Buoyancy is. I have an object that is a...
13. ### How Does the Volume of a Block Affect Its Buoyant Force?

Since they're all in the same liquid I'm assuming the buoyant forces would be the same on each block. But then I think about the volumes of the blocks, and them being different. I'm not sure if the block's volume would affect the buoyant force. Any help would be great, thanks!
14. ### Exploring the Ideal Gas Law: A Balloon Problem

Homework Statement Homework Equations Ideal gas law The Attempt at a Solution The solution to this problem assumes the pressure inside the balloon is the same as the outside pressure, i.e. atmospheric pressure. Is this a valid assumption? I would guess otherwise.
15. ### B Direction of buoyant force on sunken object?

We say that buyont force act upwards (in usual cases) and that the normal force exerted by the base of a container (of liquid) on a object is less than its true weight, so a weghing machine will give smaller reading (in terms of value) than expected. But suppose a cube sinks in water. Now water...
16. ### Which is the most efficient way to dive?

Hi Everybody! Lets say I have a sphere or an elipsoid of 10m3 full of air so it floats. I then open a valve that let's water in. At some point it will start to sink to the bottom. Let's say 100m deep. Once its down there I would like to refloat it. Which should be the most efficient method...
17. ### B Archimedes principle and the density of a rock

Hi, so I have a problem that I am working on and I think that I understand Archimedes principle but the density that I am calculating is just absurd. The problem is as follows: "A geologist finds that a moon rock whose mass is 9.28 kg has an apparent mass of 6.18 kg when submerged in water...
18. ### Archimedes Principle and steel bar question

Homework Statement Can someone tell me if i have done this correct please? A steel bar of length 0.6m and diameter 70mm is suspended from a chain and lowered into a tank of liquid whose relative density is 0.9. Determine the tension in the chain when the bar is fully immersed. The density of...
19. ### Using Archimedes' principle in engineering applications

Homework Statement A cylindrical buoy floats in sea water with its axis vertical so that it's three-fourths submerged. The buoy is 0.8m in diameter and 2m in height. Its fabricated from iron plate 10mm thick. Calculate the mass of iron chain securing the buoy. The relative density of iron is...
20. A

### Archimedes' Principle and a weather balloon

Homework Statement 2. Homework Equations Buoyant force= mg(mass of fluid displaced = Vpg (volume of fluid displaced) Buoyant force=weight of object (if floating) The Attempt at a Solution If the total mass is 99kg, then the total force acting downwards is 990N. It also said that the balloon...
21. ### I Theorem behind Archimedes principle of buoyancy?

I was thinking about why the buoyant force on an object should depend solely on it's volume and not shape. It seems loosely like the divergence theorem in that an integral over the surface is determined by the volume. There is a big difference though; in the divergence theorem we integrate...
22. ### Exploring Archimedes Principle: A Step-by-Step Demonstration

Homework Statement Hi, in my high school physics class we have to teach (part of) a lesson, mine being archimedes principle, and we have to make a demonstration of our topic. My idea was to show how you can calculate the buoyant force on a immersed object with the weight of the water it...
23. ### B Bouyancy: mass and displacement

This is something I've always wondered and I have never taught about this at school so I leave a thread on this forum. I know that displacement = the mass of the object, but I don't quite get this concept. For example, if you have a kilogram of gold and a kilogram of iron and put them in...
24. ### Weight and the Archimedes Principle

I was wondering - if you had a container of water and you push a hollow object that is buoyant to the bottom so that it is completely immersed - the whole container will be heavier because of water being displaced up in the container. Now if you release your hand or whatever you use to hold the...
25. ### B About buoyancy and 2 equations

1) My teacher says that the apparent weight of an object in water (floating,sunken,submerged etc) is equal to it's actual weight-buoyant force acting on it. That is, wt (ap)=wt (ac)- F(b) Where wt (ap) = apparent weight, weight (ac)= actual weight. And f (b) = buoyant force 2) But..., if an...
26. ### Container of Liquid Accelerated Upward

Homework Statement A block floats partially submerged in a container of liquid. When the entire container is accelerated upward, which of the following happens? Assume that both the liquid and the block are incompressible. A) The block descends down lower into the liquid. B) The block does...
27. ### I Buoyant Force and what densities to consider?

So I know FB = ρDF × g ×VDF when we submerge an object in a fluid such as water but what if we were talking about a hot air balloon? In this case would it be correct to use FB = (ρin - ρout) × g ×Vobject? Where ρin = density inside balloon and ρout = density outside balloon. If this is...
28. ### Archimedes Principle: Pure gold or not?

Homework Statement Archimedes, prove your stuff. A royal crown (cola?) of pure gold is suspended in air by a thread and the tension in the thread is of magnitude T. When the crown is totally immersed in water, the magnitude of the tension in the thread is 0.872T. A) sketch a second law force...
29. ### Fluid Mechanics and Archimedes Principle

Homework Statement [/B] A rectangular object has a width of 40 meters, height of 15 meters, and length of 2 meters. It floats consistently when 3 meters of its height is below the surface of the water. 1. Find the volume of the displaced water. 2. How much is the buoyant force on the object...
30. ### Floating block with objects that are thrown in a liquid

Homework Statement I'm confused about the following kind of situation. Consider a block of density ##\rho_b##, mass ##M_b## and section ##S_b## that floats on a liquid of density ##\rho_l##, in a tank of section ##\mathcal{S}##. On the block there are some objects (all equal), of density...
31. ### A small solid sphere of mass M0, of radius R0, and of unifor

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...
32. ### How Do You Calculate the Volume of a Floating Object?

Homework Statement If a 5kg object floats in water (density=1000 kg/m3) with 20% of it's volume above the surface of the water, what is the volume of the object? Homework Equations Archimedes' Principle = the upward buoyant force that is exerted on a body immersed in a fluid, whether fully or...
33. ### Physics Archimedes Principle Distance an object sinks

Homework Statement A block of wood measures 2.2m by 2.5m with depth 3.6m with weight 102KN. When placed in water, how far will it sink? g = 9.81 ms-2 density of water = 1000kg m-3 Homework EquationsThe Attempt at a Solution Volume = 2.2(2.5)(3.6) = 19.8m3 Mass = 102000 / 9.81 = 10398 kg...
34. ### Archimedes Principle: Calculating Relative Density for a Block of Oak and Lead

. Homework Statement A block oak weighs 90 N in air. A piece of lead weighs 130 N in water. The two weigh together 100N in water. Calculate the relative density of the wood.Homework Equations F=mxg F(archimedes)= density x Volume x g The Attempt at a Solution F (g)oak = 90 N F= mxg m= 90N/9.81...
35. ### Archimedes principle and passing gas

I used a tub for my hemorrhoid. I learned the archimedes principle which the buoyant force is equal to the mass of water displaced. The tub was filled with water 4/5. I accidently farted in a tub and suddenly the water flew into the hole which is located on the top of tub.does the fart gas...
36. ### Archimedes' Buoyancy: Which Ball Will Experience a Greater Buoyant Force?

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...
37. ### Archimedes principle boat displacement

Homework Statement 35m^3 of a boat's volume is submerged under water. What does the boat weigh? The boat is 14 metres long. Homework Equations pVg=mg The Attempt at a Solution pVg=mg pV=m m=pV=1000*35 This is what my teacher said, but I don't understand it. The submerged volume of the boat...
38. ### How Does Replacing a Sphere Affect Water Level in a Bowl?

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...
39. ### Solving Force Exerted by Liquid Using Archimedes Principle

Homework Statement Homework EquationsThe Attempt at a Solution Applying Archimedes priniciple the force exerted by liquid on the upper hemisphere would be ## F = \frac{2}{3}\pi R^3 \rho g## . Now I am not sure , what does it mean by force due to gauge pressure ? Any help is appreciated ...
40. ### Experimental Error in Archimedes Principle Lab

Homework Statement I need to find three potential reasons for my .5% error in a lab where I used the Archimedes Principle to measure the density of Iron. We only used a graduated cylinder full of water and an iron mass. I measured the water level from the meniscus. We used two different...
41. ### Water Level: Effects of New Sphere on L

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...
42. ### Solving a Physics Problem Using Archimedes Principle

Homework Statement Homework EquationsThe Attempt at a Solution On integrating the force due to fluid pressure on the cap , I have arrived at the correct result ##ρgπR^2(H-\frac{2}{3}R)## . This in turn would be the force with which the cap presses the bottom. But I would like to solve this...
43. ### Archimedes principle with a completely submerged ball

Greetings, I have a question about the classic Archimede's principle. A ball inflated with air will not sink into water. My understanding is that it will be pushed from all directions by the surrounding water trying to fill the space occupied by the ball. So there will be a pressure downwards...
44. ### Archimede's Principle and Work due to buoyant force

Homework Statement A flotation device is in the shape of a right cylinder, with a height of 0.323 m and a face area of 4.81 m2 on top and bottom, and its density is 0.460 times that of fresh water. It is initially held fully submerged in fresh water, with its top face at the water surface. Then...
45. ### Bernoulli, Fluid Dynamics, and ships

Homework Statement The Plimsoll line is a line marked on the side all ships that effectively indicates the safe maximum load the ship can carry in that type of water at that temperature.You have been asked to stand on the dock and collect the tickets of the passengers boarding a cruise ship...
46. ### Error source of SHM experiment

Homework Statement Investigating the effect of mass on the period of oscillation. This experiment is about SHM of a floating cylinder, and the theory is explained in this website: http://physics.stackexchange.com/questions/64154/shm-of-floating-objects Also, I'm attaching a diagram of my...
47. ### The possible effects on the water level

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...
48. ### Bouyancy, Archimedes principle

Homework Statement I have confusion. Suppose i have metal cube placed in empty vessel. I have seal tight the base of cube so that the water or any fluid can't seep below the cube. Now i pour water into the vessel. Will there be bouyancy on the metal cube ?? If i measure the weight of cube, will...
49. ### Calculating Buoyancy: Solving for the Height of a Boat in Salt Water

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...
50. ### Archimedes Principle - Mass floating on ice

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...