The average human has a density of 945 kg/m3 after inhalation, and 1020 kg/m3 af

Question

The average human has a density of 945 kg/m3 after inhalation, and 1020 kg/m3 after exhalation. Fresh water has a density of 1000 kg/3, sea water a density of about 1025 kg/m3, and the Dead Sea (which is actually a lake), a density of about 1230 kg/3. Which of the following statements are true?

A human would float in fresh water after exhaling.

The human body will always float in the Dead Sea.

It is easier to swim in the Atlantic than in Lake Michigan.

Without making any swimming movements, what percentage of the human body would be above the surface in sea water after exhaling?

Explanation / Answer

Given

average density of human 945 kg/m^3 , at inhalation

1020 kg/m^3 , at exhalation

fresh water density 1000 kg/m^3

sea water density is 1025 kg/m^3

dead sea (lake) density is 1230 kg/m^3

A human would float in fresh water after exhaling, that is  

ratio of densities are 1020/1000 = 1.02

if the buoyance force equal to the force of gravity then the body will floats

here it is not correct

The human body will always float in the Dead Sea

inhalation 945/1230 = 0.768 ==> 100-76.8 % =23.2 % of the body will be above the surface of water

exhalation 1020/1230 = 0.8292 ===> 100 - 82.92 % = 17.08 % of the body will be above the surface of the water

so the body will float

It is easier to swim in the Atlantic than in Lake Michigan, in correct ,

in Atlantic sea water density is less than the density of lake that is the buoyance force would be less than in lake  

so It is difficult to swim in the Atlantic than in Lake Michigan.

in sea water density is 1025 kg/m^3

1020/1025 = 0.9951 ==> 100 - 99.51% = 0.49 % of the human body would be above the surface in sea water after exhaling

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