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Thread: About Buoyancy

  1. #1 About Buoyancy 
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    I know the buoyancy is equal to the weight of displaced fluid.
    If I put a big volume object and a small volume object into water,
    the big volume object displaced more water than the low volume object.
    So,the water displaced by the big volume object is heavier than the water displaced by the low volume object.
    So, the buoyancy of big volume object are more than the buoyancy of low volume object?
    I deem yes,I want to confirm the answer.

    If an object more deeply immersed in the water,it suffered the greater buoyancy?
    Many people say wrong.....I also deem wrong.
    They say:The more the volume of an object immersed in the water,it suffered the greater buoyancy.
    I want to confirm answer only.Please explain to me.


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  3. #2 Re: About Buoyancy 
    . DrRocket's Avatar
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    Quote Originally Posted by ~James~
    I know the buoyancy is equal to the weight of displaced fluid.
    If I put a big volume object and a small volume object into water,
    the big volume object displaced more water than the low volume object.
    So,the water displaced by the big volume object is heavier than the water displaced by the low volume object.
    So, the buoyancy of big volume object are more than the buoyancy of low volume object?
    I deem yes,I want to confirm the answer.

    If an object more deeply immersed in the water,it suffered the greater buoyancy?
    Many people say wrong.....I also deem wrong.
    They say:The more the volume of an object immersed in the water,it suffered the greater buoyancy.
    I want to confirm answer only.Please explain to me.
    If by bouyancy you mean the total bouyant force exerted on an object then it is proportional to volume and therefore a "big" object will have exerted on it a greater force than a "small" object.

    If an object is deeply immersed then the bouyant force will be approximately the same as if it is not so deeply immersed, for objects and fluids that are approximately incompressible (in the ideal case of an incompressible fluid and an incompressible body there is no difference). But if the objects are compressible then you need to consider both the increase in density of the fluid with depth and the decrease in volume of the object with depth.


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  4. #3 Re: About Buoyancy 
    Forum Isotope Bunbury's Avatar
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    Quote Originally Posted by DrRocket
    Quote Originally Posted by ~James~
    I know the buoyancy is equal to the weight of displaced fluid.
    If I put a big volume object and a small volume object into water,
    the big volume object displaced more water than the low volume object.
    So,the water displaced by the big volume object is heavier than the water displaced by the low volume object.
    So, the buoyancy of big volume object are more than the buoyancy of low volume object?
    I deem yes,I want to confirm the answer.

    If an object more deeply immersed in the water,it suffered the greater buoyancy?
    Many people say wrong.....I also deem wrong.
    They say:The more the volume of an object immersed in the water,it suffered the greater buoyancy.
    I want to confirm answer only.Please explain to me.
    If by bouyancy you mean the total bouyant force exerted on an object then it is proportional to volume and therefore a "big" object will have exerted on it a greater force than a "small" object.

    If an object is deeply immersed then the bouyant force will be approximately the same as if it is not so deeply immersed, for objects and fluids that are approximately incompressible (in the ideal case of an incompressible fluid and an incompressible body there is no difference). But if the objects are compressible then you need to consider both the increase in density of the fluid with depth and the decrease in volume of the object with depth.

    Perhaps by "more deeply immersed" he is referring to partial immersion, such as a ship unladen and then laden with cargo, in which the latter case is more deeply immersed and has greater buoyancy.
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  5. #4 Re: About Buoyancy 
    . DrRocket's Avatar
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    Quote Originally Posted by Bunbury
    Perhaps by "more deeply immersed" he is referring to partial immersion, such as a ship unladen and then laden with cargo, in which the latter case is more deeply immersed and has greater buoyancy.
    Here we seem to have a problem with language.

    I think the general useage is that objects of lesser density are considered to have greater "bouyancy" -- they experience a greater net force (bouyant force less gravitational force) than a denser object.

    What is true is that a more deeply partially immersed, hence more massive object, will experiece a greater bouyant force. This is nothing more and nothing less than the statement that a floating object experiences a bouyant force equal to its weight. It if does not then it sinks.
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