Viv
Member of CYC
Posts: 430
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Post by Viv on Aug 6, 2009 19:14:28 GMT
Just been watching Extreme Fishing with Robson Green. Out in the Caribbean or somewhere, talking about catching tuna and said about "tight lines". Because the fish weigh less when in the water weigh less than when they come out. Still don't totally get it, but now sort of understand. But further explantation would be appreciated.
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ishtar
Member of CYC
Ishtar
The original Ishtar
Posts: 970
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Post by ishtar on Aug 7, 2009 6:47:22 GMT
The weght of an object in water is its weight on land MINUS the weight of the water it displaces. Water is 1kg per litre, or 1 tonne per cubic metre. Objects which are made up of largely water, such as us, or fish, weigh almost the same as the water we displace, so we are pretty much neutrally bouyant.
For more dense materials, such as concrete, metals, lead, say, they weigh many times the weight of water, so although they are lighter when in water, it is less noticeable.
btw, water is one of a very few materials where its solid form is less dense than its liquid form. That is why ice floats. If it didn't, there would likely be no fish, as when ice floats it insulates teh water, preventing further freezing. If it sunk, the freezing would continue, until it was solid, killing the fish.
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Viv
Member of CYC
Posts: 430
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Post by Viv on Aug 7, 2009 12:51:11 GMT
Oooh! Blinding me with science a bit there! Still don't fully get the bit about tight lines though! Might have to explain in words of one syllable!
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