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Old Nov 21st 2017, 03:58 AM   #1
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Raft - Floating / Density problem

A raft is 200kg.When raft is empty it float on water by 60%
of the volume immersed.John weighs 75kg. Can he sit on the raft without it sinking?How much load can the raft take before it's completely under water?
What is the density of the raft?
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Old Nov 21st 2017, 07:10 AM   #2
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How much of the empty raft is below water?
This is the amount of water that is displaced by the empty raft.

What is the mass (weight) of the displaced water?
Hint: this will be the amount needed to balance a 200kg raft.

Add John; the mass of the raft + John rises to 275 kg.
How much more water will need to be displaced to balance the raft + John?
How much lower will the raft have to float to displace this amount of water?

If you can answer these questions you should be well on the way to answering the whole problem.

I think that you can only determine the density of the raft if you know the density of water.
This is a well known standard value (part of the definitions of the standard kilogram and the standard litre).
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Old Nov 22nd 2017, 02:15 PM   #3
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Thanks.
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