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.
- The hydrostatic weighing container above is filled with water. If point A is 0.7 m above the bottom of the container, what is the fluid pressure at point A? (Note: The density of water is 1,000 kg/m³.)

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.
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The hydrostatic weighing container above is filled with water. If point A is 0.7 m above the bottom of the container, what is the fluid pressure at point A? (Note: The density of water is 1,000 kg/m³.)

Quizplus · Accepted Answer

11ecba2d_12f7_b16e_a3bf_1be78906f996_MD0008_00 Hydrostatic pressure is the pressure exerted by the weight of a static (nonmoving) fluid. Its magnitude is the product of the fluid density ρ, the gravitational acceleration g, and the height h of the fluid above the point of interest: 11ecba2d_12f7_b16f_a3bf_7feed7e384ce_MD0008_00 From the given figure, the height of the fluid above point A is the difference between the total height and the height of point A given in the question: 11ecba2d_12f7_b170_a3bf_ebbbe98c7837_MD0008_00 Hydrostatic pressure is calculated using the value of ρ_water given in the question, the value of g given in the passage, and the height h of 1.3 m: 11ecba2d_12f7_b171_a3bf_51774b553665_MD0008_00 Converting to scientific notation, the hydrostatic pressure at point A is 1.3 × 10⁴ N/m². (Choice A) The hydrostatic pressure exerted by the height of the fluid below point A (h = 0.7 m) is 7.0 × 10³ N/m². (Choice B) The weight (not the pressure) of the fluid above point A is calculated by W = ρVg = 1.0 × 10⁴ N. (Choice D) The hydrostatic pressure measured at the bottom of the container (the pressure exerted by the full height of the fluid, 2.0 m) is 2.0 × 10⁴ N/m². Educational objective: Hydrostatic pressure is the pressure exerted by the weight of a static fluid. It is the product of the fluid density ρ, the gravitational acceleration g, and the height of the fluid above a given point h: P = ρgh.

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