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MECHANICS OF FLUIDS

Buoyancy: the ability of a body to float

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Archimedes’ Principle: When an object is submerged in a fluid, it receives an upward

force called buoyancy. The buoyancy force is equal to the weight of the displaced water.

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density = mass / volume

density of fresh water = 1 kg/liter

if density <1 the body floats in fresh water

if density >1 the body sinks in fresh water

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materials of human body:

density (kg/l)

fat ≈ 0.8

muscle ≈ 1.1

bone ≈ 1.5

air 0.0012

In fresh water:

ocean water density ≈ 1.026 kg/l

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Center of buoyancy

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Lift and drag forces

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drag force

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Factors that affect the drag force

Larger speed larger drag force

Larger frontal area larger drag force

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Shape of object

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Roughness of surface

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lift force

discus:

frisbee:

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Magnus effect

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soccer kick with Magnus effect: