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Thread: The spring buoyancy

  1. #1 The spring buoyancy 
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    Hello,world

    1-How does this spring scale work?

    2-Where does this increase in the reading of the normal balance(scale) come from?
    Does it come from the rise in water level in the tank?Okay water already has aconstant mass

    Does it come from the weight of the ball?I don't think so.

    3-why does the apparent weight decreases as the ball goes down into the fluid(by increasing depth)??may be because the buoyant force increases..
    the buoyant force is different in case(2) and case(3) although the ball already displaced the same volume of water-so buoyancy should be the same.can you realise my problem here?

    4-In case(3)
    The spring reads zero
    which means that Fb=Fg
    so the body should suspend in water instead of sinking ...or may be the spring is exerting a certain force to maintain the ball in this position.may be this question is related to the first one which is concerned with the mechanism of the spring balance

    5-can we know from this picture if the spring has a smaller-equal-bigger density than that of water?or it just doesn't indicate?

    Thanks in advance


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  3. #2  
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    hello there?


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    Twinkle...Twinkle little star ...How I wonder what you are

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    Up above the world...so high....like a diamond in the sky...
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  4. #3  
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    The tank of water weighs 50, the ball weighs 20. Total weight is 70, so the sum of the 2 scales is always 70. When the ball is floating in the water, the weight of the ball is supported by the water, via the buoyant force, and this adds to the normal scale reading while subtracting from the spring scale reading. In case 1 the ball is either light enough to float, or is resting on the bottom of the tank. In either case, its weight is fully supported by the scale which is weighing the water tank. In case 2 the ball is denser than the water, so it does not float but is partly supported by buoyant force. In case 3 the ball is partially withdrawn from the water, so there is some buoyant force but less than the fully submerged ball. In case 4, the ball is out of the water so its weight is supported by the spring scale.
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