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| Floating and Sinking |
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| Let W = Vrg be the true weight of body, acting through the centre of gravity and let 'w' be the weight of the liquid displaced, acting through the centre of gravity of the displaced liquid (called the centre of buoyancy). |
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| W-w = observed weight of the body immersed in a liquid (or fluid). |
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| If W>w, then W-w is positive and the body sinks to the bottom of liquid. This is seen when a stone is held below water, it sinks when it is released. |
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| If W |
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| If W=w, then W-w is zero, the upward force is equal to the weight of body in air. |
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| In the last case, the body floats. Hence, according to the law of floatation. |
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| A body will float in a liquid if the weight of liquid displaced by immersed part of the body, is equal to or greater than weight of the body. |
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| The diagram depicts the centre of gravity (G) and centre of buoyancy (B). For a floating body to be stable, the centre of gravity should lie vertically below the centre of buoyancy as shown in fig (b). |
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