Teaching Physics with the Physics Suite

Edward F. Redish

Home | Action Research Kit| Sample Problems | Resources | Product Information

Problems Sorted by Type | Problems Sorted by Subject | Problems Sorted by Chapter in UP

Designing a life vest

People have a variety of different body types – ectomorph, mesomorph, and endomorph. Ectomorphs are slim and lightly muscled and they have a high average body density, mesomorphs are more heavily muscled and have little body fat, while endomorphs have more body fat and a lower average body density. You are designing a life jacket that should keep an individual of any body type afloat even when that individual might be unconscious. The life jacket shown is filled with low density PVC foam that has a density of about 0.2 g/cm3. An ectomorph might have a body density as high as 1.3 g/cm3. Explain your answers.

A. Find the volume of a 100 kg high-density ectomorph.

B. How much additional volume would he need so that the buoyant force of the water would keep him afloat in fresh water (density of 1.0 g/cm3)?

C. What volume of PVC would be needed in the vest to give this much buoyant force?

Page last modified December 12, 2009: M28