To determine an athlete's body fat, she is weighed first in air and then again while she's completely underwater. It is found that she weighs 690 N when weighed in air and 36.0 N when weighed underwater. What is her average density?

Answer 1

m g = 690

mg - 1000 kg/m^3 * V g = 36

1000 V g = 690 - 36 = 654 N
g = 9.8
so
V = 654/(1000 g)

rho = m/V = 690/g / .654/g = 1055 kg/m^3
just a little heavier than water (must have expelled all air from her lungs to sink like that)

Answer 2

IDK I kill cats for a living