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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: