Why is it inaccurate to say that heavy objects sink and light objects float?

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  • Why is it inaccurate to say that heavy objects sink and light objects float?


Answer #1 | 11/02 2014 06:26
Because the medium that a given item is immersed in - that item being 'heavy' or 'light' - has not been specified. For example, whether an item will float on the surface of a liquid, sink in that liquid, or remain suspended in that liquid is determined by the densities of that liquid and the density of that item. If the density of that item is greater than the density of that liquid, the item will sink; if the density is less, it will float on the surface; if equal, it will neither sink nor float: it will remain suspended in that liquid. You can prove that to yourself without getting into formulas and mathematics. Imagine one cubic metre of water that is within a tank of water which contains many cubic metres of water. The density of the cubic metre of water (the 'item') and density of the water in the tank (the 'medium') are equal - so the 'item' remains suspended in the medium. Now replace that 'item' with something of the same volume (1 cubic metre) by something heavier - say a block of lead. Lead has a density much greater than water - so the lead sinks. Now replace the 'item' by a plastic bag (of 1 cubic metre volume and with very thin walls) which is filled with air. Air has a density much less than water - so the bag floats to the surface. If the water is now replaced by any other medium - say air, petrol, sea-water, etc., the same reasoning applies. For example, bodies that just sink in pure water are found to float in water that has a lot of salt dissolved in it: the salt increases the density of the water - so the item now floats. Hope that helps.
Answer #2 | 11/02 2014 06:03
Boyancy makes that inaccurate
Answer #3 | 11/02 2014 06:04
because sinking of an object depends upon its shape.
Answer #4 | 11/02 2014 20:55
Because you should be saying objects denser than the medium they are floating in sink and those less dense float. It's not how heavy they are, it's how much density of the liquid (medium) that suspends it is displaced. If a 100,000 ton boat displaces 150,000 tons of water, it floats.

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