Archimedes principle Definition and 106 Threads

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. L

    Archimedes Principle and Buoyancy

    Homework Statement A 100g object having a density less than that of water is placed into a beaker half full of water. The beaker is then placed on a triple beam balance. Would be measured weight be equal to, greater than, or less than the weights of the water, the beaker, and the object added...
  2. A

    Archimedes Principle Problem: Floating Object

    Homework Statement A cylindrical log of uniform density and radius R=30.0cm floats so that the vertical distance from the water line to the top of the log is d = 12.0cm. What is the density of the log? Homework Equations Fbouyant=Wwaterdisplaced ρwater * V displaced water = ρlog *...
  3. A

    Hot air balloon - Archimedes Principle

    Homework Statement A hot air balloon with V = 500 m^3 is floating in the air without moving. The air outside the balloon has a density of 1,20 kg/m^3, and the hot air inside the balloon has a density of 0,75 kg/m^3. Calculate the total mass of the hot air balloon. Homework Equations...
  4. L

    Archimedes principle - special case

    Homework Statement We have a chinese lantern (balloon) made of paper, cylinder shaped with the following sizes: base diameter - 45 cm, height - 70 cm. Mass of the balloon is 57 g (21 g from this is mass of "fuel" - the fuel is wax paper!). Fuel is then ignited at the centre of the base, which...
  5. N

    Newton's Second Law / Archimedes Principle

    Homework Statement A block of wood floats in fresh water with 0.722 of its volume V submerged and in oil with 0.895 V submerged. Find the density of (a) the wood and (b) the oil. Homework Equations mass = density x volume f = ma conservation of mass F_{weight} - F_{buoyancy} =...
  6. A

    Archimedes principle vs Atwood's principle

    If we have an upward moving sphere with 0.4 m3 volume and 100 kg mass , according to Archimedes buoyancy force = 4000 N so acceleration = 40 m/s^2 But according to Atwood's principle , buoyancy force ≈ 1600 N acceleration = 16 m/s^2 what makes such big difference . ( ignore drag force and...
  7. A

    Archimedes principle and shapes of the body

    Archimedes principle of the force of upthrust = weight of water displaced by the body immersed , but is this law independent of the shape of this body. If we use the idea that the upthrust = P*A on the lower side - P*A on the upper side , if we use it on a rectangle or a square , the only change...
  8. K

    Buoyancy Situation Doubt - Archimedes Principle

    Hi to all, i will appreciate your help in this. This is the situation: I have a tank, with a water column in it. This tank at the bottom has an "ideal" seal (a seal that permit the passing of object from bottom to upwards, but not the water to fall down.) In this system i have sphere with...
  9. P

    Buoyancy and Archimedes Principle, volume ratio/density question

    A geode is a hollow rock with a solid shell and an air-filled interior. Suppose a particular geode weighs twice as much in air as it does when completely submerged in water. If the density of the solid part of the geode is 3100 km/m^3 , what fraction of the geode's volume is hollow? The...
  10. D

    Question about the Archimedes principle and gravity.

    Hello, I was taking a shower and started to think about balloons and helium and this question came to me: Wouldn't the things on Earth be lighter than say, a similar planet (same gravity) but with no atmosphere? (because of the push from air) I googled it but I am not sure of using the correct...
  11. K

    Archimedes Principle: B = δVg + T

    Hi :) When I have a container with water and put a piece of metal down in the water while it's hanging on the string, I know that there will be two forces pulling it upwords: B = δVg and the string force T But the force pulling it down, is that the gravitation? Or is it a force that...
  12. S

    Solved: Calculating Force Needed for Archimedes' Principle

    Homework Statement A solid cube of foam plastic has a volume of 25m^3 and a density of 800kg/m^3. How large a force is required to hold it under water? Homework Equations P = F/A Fb = ρgV ρ = m/V The Attempt at a Solution ρ = m/V 800 = m / 0.000025 m = 0.02kg so F = mg = 0.02...
  13. S

    Understanding the buoyant force in archimedes principle

    I'm really confused about the buoyant force. What I've understood is that the buoyant force of an object is equal to the volume of the displaced fluid even if it is floating (not fully immersed in the fluid). How can this be possible? The volume of the object is the amount of water displaced...
  14. V

    Working with archimedes principle.

    Homework Statement Consider a submarine inside an ocean. It's bottom is flat and upper portion is hemispherical. It is settled at the bottom of the sea. What should direction of Boyant force. Upward or downward? Now by the external agent the submarine is lifted a bit up. Now it is not touching...
  15. V

    Question on Archimedes principle.

    Homework Statement A solid sphere of mass m=2 kilogram and specific gravity s=0.5 is held stationary to a tank as shown in figure. The tank is accelerating upward with a=2ms-2. calculate the tension in the string? If suddenly string break then the acceleration of the ball in frame of tank...
  16. V

    Fluid: Archimedes Principle Homework Question

    Homework Statement A Kennedy half-dollar has a mass that is 1.150 x 10-2 kg. The coin is a mixture of silver and copper, and in water weighs 0.1011 N. Determine the mass of silver in the coin. Homework Equations Explicit givens: m = 1.150 x 10-2kg apparent weight =...
  17. P

    Calculating Density Using Archimedes Principle

    I have found a question that has got to my nerves : A block of wood of length 40 cm and area of cross-section 15 cm2 floats in water with 3/8 of it's length above water. What is the density of wood ? (Density of water - 1g/cm3). My attempt to get the solution : Length of wood above...
  18. L

    I don't understand Archimedes principle

    Homework Statement The problem is I have about 13 questions to do, but I don't understand Archimedes principle when my teacher was supposed to teach it at school, all he did was send notes... I do extra classes for Physics, the teacher there taught it, I understand a little better...
  19. L

    Calculating Relative Density and Apparent Weight Using Archimedes Principle

    Homework Statement A piece of sealing-wax weighs 0.27 N in air and 0.12 N when immersed in water. Calculate : a) It's relative density b) It's apparent weight in a liquid of density 800 kg/m^3 The attempt at a solution I did part a) I got 1.8 I have no idea how to attempt part...
  20. M

    Questions on Archimedes principle

    1-A hollow ball is suspended in water,has a larger density than the density of the water..how? Fb=Fg (okay) ρ(of water)* (Vol of ball substance+Vol.of the cavity)=ρ(of the ball) * vol of the ball substance) (not okay) I don't understand how we calculate the buoyant force The buoyant...
  21. U

    Gravitation and Archimedes principle as a spring?

    Hey all, I have seen that these two forces combined together have the potential energy of a spring with a constant 'K' as a combination of some sort of the two forces. I have no idea how am I to find this K. All I know Mgh + ρVgh gives the potential energy of a given system let's say. help?
  22. K

    Archimedes Principle to determine height of continental crust

    I'm taking an introductory geology class and am having big trouble with the math questions, as it's been many many years since I last took math classes. I am to use Archimedes Principle to calculate the thickness of continental crust beneath a certain coastal geographical point (at sea level...
  23. F

    Solving Archimedes Principle Homework: Understanding Derivation

    Homework Statement trying to make sense of this derivation... Homework Equations Buoyant force is not an independent force but is derived from difference in pressure from the bottom of an object to its top. Lets say an object of density "ρ'" is located "d" meters down the surface of a...
  24. R

    Archimedes Principle, Buoyant Force

    Homework Statement Your local king has asked you to determine the density of a crown. If you suspend it from a spring scale, the scale reads 8.33 N. If you then lower the statue into a tub of water, so that it is completely submerged, the scale reads 7.81 N. What is the density of the...
  25. M

    How much of an iceberg is beneath the surface Archimedes principle

    How much of an iceberg is beneath the surface...Archimedes principle Homework Statement Calculate how much of an iceberg is beneath the surface of the ocean, given that the density of ice is 917kg/m^3 and salt water has density 1025kg/m^3. Homework Equations archimedes principle...
  26. P

    How Much Helium Is Needed to Lift a 340kg Balloon?

    Homework Statement How much helium (density 0.18) is requires to lift a 340kg balloon. density of air is 1.28 Homework Equations The Attempt at a Solution\ i don't know why i keep getting the wrong answer buoyant force required is 340g which = rho g V and i keep getting...
  27. P

    Solving Archimedes Principle: 6500kg Iceberg in Sea

    Homework Statement a 6500kg iceberg is afloat in the sea. the icebergs density is 930kg/m^3 and the sea water has density of 1030kg/m^3 a) find the buoyant force on the iceberg the volume of water displaced and the fraction of the icebergs volume that is below the waterline. Homework...
  28. P

    Archimedes Principle and hanging block

    Homework Statement 9. Block A hangs by a cord from spring balance D and is submerged in a liquid C contained in beaker B. The mass of the beaker is 1.00 kg; the mass of the liquid is 1.80 kg. Balance D reads 3.50 kg, and balance E reads 7.50 kg. The volume of block A is 3.80  10-3 m3. (a)...
  29. J

    Archimedes Principle Quick Question

    Homework Statement In air, Bob's weight is 687 N. In water, it is 34.7 N. Determine Bob's average density. Homework Equations The Attempt at a Solution Is it correct to say that (buoyancy force) + 34.7 N = 687 N? If so then buoyancy force = (density of water)(volume)*9.81...
  30. S

    Fluids Archimedes principle apparent weight question

    Homework Statement Vessel contains water.It is placed on the pan of a physical balance.A solid(specific gravity=1) is suspended from an thread(from an independent support),such that it is immersed completely in the water. What the weight it reads? If the thread was tied to the arm of...
  31. A

    Is Archimedes principle violative of Newton's 3rd law of motion?

    1. When a heaveir body having density more than water, is submerged in water, as per Newton's third law of motion, it experiences an equal & opposite thrust i.e. an upward thrust equal to its weight. Then, the body should have remained afloat, but, we find it sinks. Is it not violative of...
  32. N

    Calculating density Archimedes principle

    I have to calculate the density of these 3 objects and these are the values i obtained but now i am confused how i can calculate the density of them. I know that in chemistry density is mass / volume but in this case i am not sure, can anyone tell me the formula? thanks in advance
  33. C

    What is the density of the body in Archimedes' Principle problem?

    Hello all! Inside the water, body weights two times less than in air. Density of water is 1000kg/m^3. Find the density of body. 1. Well I tried this solution and I'm not sure if it's correct. I started from this principle Fa=W/2 (inside water force equals weight of the body divided by...
  34. J

    How Much Does the Water Level Rise with a Submerged Object?

    An object weighs 30kg in air it is lowered into a square tank (1m x 1m) the weight of the object in the water is 16kg. how much does the water level in the tank raise? Heres my attempt. 30-16 = 14kg 14kg = 14 m^3 1 x 1 x h = 14 h = 14 metres. Is this correct it doesn't seem...
  35. J

    Solve Archimedes Principle: 800kg Load on 5x2m Barge in Fresh Water

    Homework Statement A rectangular barge, 5 meters long and 2 meters wide, floats in fresh water. How much deeper will the barge sink when a 800 kg load is added to the barge? Use a density of water of 1000 kg per cubic meter. Homework Equations not sure The Attempt at a...
  36. W

    Archimedes Principle and Specific Gravity Determination

    Homework Statement a crown that is supposed to be pure gold has a mass of 850g. Its apparent mass when immersed in water is 798g. (a) what is the volume of the crown? (b)is it pure gold?If not, what is the percentage by volume of gold in the crown assuming that the crown is an alloy of lead and...
  37. djeitnstine

    Why Does the Styrofoam Slab Float at Water Level When a Swimmer Rests on It?

    This (textbook) question seems so simple yet I have been having the hardest time solving it :S I know there's something completely obvious I'm missing. Homework Statement A styrofoam slab has a thickness h and density \rho_{s}. When a swimmer of mass m is resting on it, the slab floats in...
  38. A

    Archimedes Principle: Find Vol, Bouyant Force & Density of Plank

    Homework Statement Find: (a) volume of plank (b) bouyant force (c) density of plank mass plank = 877kg mass bricks loaded on plank = 2.3 * 74 = 170.2 plank if floating level with surface of lake Homework Equations p = m/vol v = l w h Fb = pfluid x g x volume The Attempt at a...
  39. B

    Trying to find volume given Newtons/ archimedes principle

    Homework Statement A paperweight, when weighed in air, has a weight of W = 6.6 N. When completely immersed in water, however, it has a weight of Win water = 4.0 N. Find the volume of the paperweight. Homework Equations Fb = Wfluid The Attempt at a Solution I can find density...
  40. M

    Calculating Weight to Make Balloon Rise 116m in 17s Using Archimedes Principle

    A lighter-than-air spherical balloon and its load of passengers and ballast are floating stationary above the earth. Ballast is weight (of negligible volume) that can be dropped overboard to make the balloon rise. The radius of this balloon is 6.59 m. Assuming a constant value of 1.29 kg/m3 for...
  41. H

    Archimedes Principle & Specific Gravity

    I was reading a lab online and I came across one that dealt with Specific Gravity and Buoyany and stuff.. and then they had these equations: *Note: p = density, M = mass, V = Volume, g = gravitational acceleration, W = Weight Subscripts: S = substance, W = water SG = pS / sW = (MS / VS)...
  42. S

    How Is Tension Calculated for a Submerged Accelerating Object?

    Homework Statement A lead weight with a volume of 0.69x10^-5 m^3 is lowered on a fishing line into a lake to a depth of 1.0m. What tension is required in the fishing line to give the weight an upward acceleration of 1.8m/s^2? Homework Equations T=F-mg F=ma D=mv D of lead= 11.34gcm^3...
  43. B

    Archimedes Principle and bouyant force

    Hello: Can someone help with the following 2 questions? 1. An iron casting containing a number of cavities weighs 6000 N in air and 4000 N in water. What's the total volume of all cavities in casting? The density of iron without cavities is 7.87 g/cm^3. The density of water is 988...
  44. Z

    Archimedes principle and relativity

    Is there any relativistic version for Archimedes principle?
  45. J

    Archimedes principle problem? *1 fluid, 1 solid*

    I'm having trouble arriving at a finalized answer dealing with the sum of the forces with this problem dealing with Archimedes principle (buoyancy is weight of the displacement). Here's the question: A cube of wood whose edge is 12 mm is floating in a liquid in a glass with one of its...
  46. Y

    Understanding Fluid Displacement: The Difference Between Floating and Sinking

    Homework Statement A fisherman and his young nephew are in a boat on a small pond. Both are wearing life jackets. The nephew is holding a large helium filled balloon by a string. Consider each action below independently and indicate whether the level of the water in the pond, Rises, Falls, is...
  47. H

    Archimedes principle free fall problem

    I have 2 question about the Archimedes principle? 1. does it hold in a vessel in a free fall? why? 2. if we imppressed 2 same hollow bodies in water, and just one of them has a hole at the bottom. which one is more difficult and why? thank you!
  48. R

    How Did Archimedes Use His Principle to Compare Densities of Gold and Silver?

    Can somebody explain Achimedes principle to me? Where he used it to determine the difference in density between silver and gold. Apparently he immersed a lump of gold and silver in water (I assume they were the same size/volume) and each lump displaced a different volume of water. Is that the...
  49. G

    Understanding Archimedes Principle: X1 Height in Mercury & Water

    Alright.. I have a problem. I have 2 liquids, mercury and water together in the beaker. Assuming both liquids are non mixable, the water, with a lower density, will be at the top while mercury will be at the bottom. Now, I push a block into the water and it floats at halfway between...
  50. U

    Archimedes Principle and resonance

    i got 2 qn , 1 on archimedes principle and the other on resonance 1)The Artic Ice cap is a floating ice mass. If the ice were to melt, how would the depth of the ocean change? my ans was that it will become deeper but the ans was it will remain the same...why? 2) my understanding is...
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