Archimedes Principle: Weight of Immersed Object

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  • Thread starter Deebu R
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In summary, Archimedes' principle states that the buoyant force on an object is equal in magnitude to the weight of the displaced liquid. For a partially immersed object, there may be other forces at work in addition to gravity and the buoyant force. In a situation where there is equilibrium, the weight of the water displaced will be equal to the weight of the entire object. However, if there are other external forces at play, the weight of the displaced water may be different than the weight of the object.
  • #1
Deebu R
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I was just a bit confused about Archimedes principle. Say an object is partially immersed in water. The weight of water water displaced will be equal to weight of the entire object or just the part immersed in water?
 
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  • #2
Archimedes' principle states that the buoyant force on an object is equal in magnitude to the weight of the displaced liquid.

A corollary is that for a freely floating object on the surface, the buoyant force must exactly cancel the weight of the object. Since Archimedes' principle states that the buoyant force is equal in magnitude to the weight of the displaced liquid, the weight of the displaced liquid must be equal to the weight of the entire object or the object will not be floating.

Note that freely floating in not the same as partially immersed. For a partially immersed object, there may be other forces at work as well in addition to gravity and the buoyant force. In that situation, those forces must also be taken into account.
 
  • #3
It depends: on whether there is equilibrium ! If you have to push down to keep a cork partially under water, the weight of the water is more than the weight of the cork. And if you have to pull up to keep a block of concrete halfway in the water, the weight of the water is less than the weight of the concrete.

But if a boat floats peacefully on the surface, then yes: the volume of water displaced weighs as much as the wole boat
 
  • #4
Ah.ok. I understand. Thank you orodruin and BvU.
 
  • #5
One more thing. Is there a case were the weight of water displaced equal the weight of the part of the body which is below water level?
 
  • #6
Deebu R said:
One more thing. Is there a case were the weight of water displaced equal the weight of the part of the body which is below water level?
Yes, when there is nothing above the surface and the object has the same mean density as water.

Or when the remaining force to hold the object in place is provided by another external force.
 
  • #7
I understand. Thank you
 

What is Archimedes principle?

Archimedes principle states that the buoyant force acting on an object immersed in a fluid is equal to the weight of the fluid that is displaced by the object.

What is the weight of an immersed object?

The weight of an immersed object can be calculated by multiplying the density of the fluid, the volume of the displaced fluid, and the acceleration due to gravity.

How does Archimedes principle relate to the flotation of objects?

Archimedes principle explains why objects float or sink when placed in a fluid. If the weight of the object is less than the weight of the displaced fluid, the object will float. If the weight of the object is greater, it will sink.

What are some real-life applications of Archimedes principle?

Archimedes principle is used in various applications such as designing ships and submarines, determining the density of an object, and calculating the weight of an object in water.

How does the density of an object affect its buoyancy?

The density of an object affects its buoyancy because the more dense an object is, the more it will sink in a fluid. This is because the buoyant force acting on the object is equal to the weight of the displaced fluid, and a denser object will displace less fluid.

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