Passage
Hydrostatic weighing is a technique used to determine an individual's overall body density. The weight of the individual is measured when their body is completely submerged in water. Because the volume of air in the respiratory system affects the measured underwater weight, the individual must exhale completely before entering the water. However, residual volume, the volume of air that always remains in the respiratory system, must also be accounted for.By comparing an individual's in-air weight to their underwater weight, their total body volume can be determined. The density of the body D_b excluding any air in the respiratory system is calculated with the in-air mass of the individual m_air, the individual's total body volume V_total, and an estimate of residual volume V_res by:
Db=mairVtotal-VresEquation 1Body density can be used to calculate an individual's body fat composition, the percentage of total body mass that is made up of fatty tissue. Human fatty tissue has an average density of 0.9 kg/L, and the density of water is 1 kg/L. The acceleration due to gravity is 10 m/s².
Adapted from Siri, WE, Body composition from fluids spaces and density. Nutrition 1956 Springer Nature.
-An individual that weighs 700 N in air has an apparent weight of 40 N when submerged in water. What is the volume of the displaced water?

Question

Passage
Hydrostatic weighing is a technique used to determine an individual's overall body density. The weight of the individual is measured when their body is completely submerged in water. Because the volume of air in the respiratory system affects the measured underwater weight, the individual must exhale completely before entering the water. However, residual volume, the volume of air that always remains in the respiratory system, must also be accounted for.By comparing an individual's in-air weight to their underwater weight, their total body volume can be determined. The density of the body D_b excluding any air in the respiratory system is calculated with the in-air mass of the individual m_air, the individual's total body volume V_total, and an estimate of residual volume V_res by:

Db=mairVtotal-VresEquation 1Body density can be used to calculate an individual's body fat composition, the percentage of total body mass that is made up of fatty tissue. Human fatty tissue has an average density of 0.9 kg/L, and the density of water is 1 kg/L. The acceleration due to gravity is 10 m/s².
Adapted from Siri, WE, Body composition from fluids spaces and density. Nutrition 1956 Springer Nature.
-An individual that weighs 700 N in air has an apparent weight of 40 N when submerged in water. What is the volume of the displaced water?

Quizplus · Accepted Answer

11ecba2d_12f6_2abd_a3bf_3f7573a59342_MD0008_00 According to Archimedes principle, a submerged object experiences an upward buoyant force due to the displaced fluid. Therefore, an object will appear to weigh less than its in-air weight W_air when submerged in water, and this is the object's apparent weight W_apparent: 11ecba2d_12f6_2abe_a3bf_f717d58ac0d3_MD0008_00 The buoyant force acting on the individual is the difference between W_air and W_apparent given in the question: 11ecba2d_12f6_2abf_a3bf_9b00b9275383_MD0008_00 11ecba2d_12f6_51d0_a3bf_ef20f40bbdb1_MD0008_00 From Archimedes principle, the buoyant force experienced by the individual is equal to the weight of the displaced fluid, which is the product of the density of water ρ, the displaced volume V, and the gravitational acceleration g: 11ecba2d_12f6_51d1_a3bf_a54982e0afb1_MD0008_00 The volume V displaced by the individual is calculated using the values of ρ_water and g given in the passage: 11ecba2d_12f6_51d2_a3bf_19dcfe2a121e_MD0008_00 11ecba2d_12f6_51d3_a3bf_9ffc0f8a0f8e_MD0008_00 The volume of the displaced water is 66 L. (Choice A) The apparent weight of the individual (40 N) is not equal to the buoyant force; the individual's apparent weight is the difference between the individual's in-air weight and the buoyant force. (Choice D) An amount of 70 L of displaced water would result in a buoyant force of 700 N. The buoyant force is equal to the in-air weight of the individual only if the individual is floating at the surface or if the individual was suspended (neither rising nor sinking). Educational objective: The apparent weight of a submerged object is its reduced weight due to an upward buoyant force. The buoyant force is equal to the weight of the displaced fluid, which is the product of the fluid's density ρ, volume of displaced fluid V, and the gravitational acceleration g: F_B = ρVg.

Passage Hydrostatic Weighing Is a Technique Used to Determine an Individual's