Physics
posted by Meg .
In an immersion measurement of a boy’s density, he is found to have an apparent weight of 6.86N when completely submerged in water with lungs empty. The mass of the boy is 68.0kg in air. The density of water is 1000kg/m^3.
a)Determine the density of the boy;
b)Will the boy float in sea water (density of sea water is 1029kg/m^3)? If yes, what percentage of his body volume will be above sea water?

Physics 
Damon
6.86 = m g  1000 g V
g = 9.81 m/s^2
6.86 = 9.81 (68)  9810 V
9810 V = 660
V = 66/981 m^3
m = 68
so m/V = (68/66)981 = 1011 kg/m^3
===============================
In seawater
volume of boy = 66/981
so mass of water displacedd submerged =
1029*66/981 = 69.2 kg
BUT
boy only has mass of 68 kg
so he floats
fraction above = (69.2  68) /68
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