Basic Physics. Scalar magnitude Vector magnitude and direction.
Intermediate Physics for Medicine and Biology - Chapter 1 ... · Distances and Sizes Valuable skill...
Transcript of Intermediate Physics for Medicine and Biology - Chapter 1 ... · Distances and Sizes Valuable skill...
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Intermediate Physics for Medicine and
Biology - Chapter 1
Professor Yasser M. Kadah
Web: http://ymk.k-space.org/courses.htm
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Biological Object Sizes
a) A paramecium
b) An alveolus
c) A cardiac cell
d) Red blood cells
e) Escherichia coli
bacteria
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Biological Object Sizes
a) Human
immunodeficiency
virus (HIV)
b) Hemoglobin
molecules
c) Cell membrane
d) DNA molecule
e) Glucose molecules
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Approximate Sizes of
Biological Objects
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Distances and Sizes
Valuable skill in physics: ability to make
order-of-magnitude estimates
Example: Calculate number of cells in body
Cells ~ 10 m in size → volume ~ (10 m)3
Adult ~ 2 m tall and 0.3 m wide
→ volume ~ 2 × 0.3 × 0.3 = 0.18 m3
Assume body is made entirely of cells
Number of cells = 0.18/1e-15 ~ 2 × 1014
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Forces and Translational
Equilibrium
Force defined by Newton’s second law
Translational equilibrium:
Equilibrium:
remains at rest
move at constant speed
i
i 0F
maF
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Rotational Equilibrium
Torques i is defined as
Rotational equilibrium if,
iii Fr
i
i 0
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Example: Achilles Tendon
Apply both translational and rotational
equilibrium conditions
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Example: Forces on the Hip
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Example: Use of a Cane
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Work
Work done by a force Fx as it moves
from x1 to x2
Area under curve
Equal to increase in K.E.
2
1
)(
x
x
x dxxFW
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Stress and Strain
Normal stress: tensile/compressive
E: Young’s modulus
l
lEE
S
Fs nn
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Shear
Force parallel to surface
G: shear modulus
hGG
S
Fs ss
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Hydrostatics
Equilibrium:
g
dz
dp
gzpp o
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Buoyancy
Object immersed in fluid
Example: Terrestrial animals
Very small buoyancy because
Example: Aquatic animals
Very small F because
“Weightless” in water
VgF fluid )(
fluid
fluid
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Compressibility
Pressure on a fluid
Compressibility negligible in many cases (e.g., =5×10-10 Pa-1 for water)
Important for such phenomena as ultrasound transmission
pV
V
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Viscosity
Laminar flow of a Newtonian fluid
Application: clean room isolation
dy
dvSF x
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Pressure-Volume Work
Work done by a gas
dVpdxSpdxFW gasby
2
1
V
V
gasby dVpW
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Example: Respiration Work
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Circulatory System
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Turbulent Flow and
Reynolds Number
Turbulent flow when Reynolds number
is more than a few thousands
LVNR
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Problem Assignment
Posted on class web site
Web: http://ymk.k-space.org/courses.htm