Transcript Chapter 1

Dynamics
Instructor:
S.A.A.Oloomi
Email: [email protected]
Text: "Dynamics", Meriam and Kraige, 5th Edition,
Wiley, 2001. The course will follow closely the material
developed in the text, but sometimes from a different
refrences.
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Mid Term: 8 Points
Final Exam: 12 Points
Quiz & Homework: 2 Points
Sum: 22 Points
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Dynamics
Dynamics is broadly defined as the study of how materials
change their properties with respect to time. The field of
dynamics is one of the oldest and most fundamental in all of
engineering. Different subfields of dynamics study the change in:
1) Position, velocity, acceleration of electrons, mass bodies in space
2) Material properties (mass, magnetization, density, temperature)
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Introduction to Dynamics


F  ma
Above is the well-recognized Newton’s 2nd law of motion.
Note: This is an experimental law and is not “proven”, but merely
reflects the most concise statement on the collection of physical
experiments to date.
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Units/Dimensions of Force
• Dimensions
• Units
= (mass*length)/(time)2
= Newtons  kg 
= lbf  slug 
ft
s
m
s
2
2
SI units
English units
kg=kilogram
lbf=pound of force
m=meter
ft=feet
s=second
lbm=pound of mass, or slug x g
g=9.8 m/s2
g=32.2 ft/s2
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Famous Law of Gravitational
force

G
12
F
m1 m 2
1
  G  2 rˆ12  Gm 1 m 2  
r12
r12

r12
m2

r2
m1
G  6 . 673  10
Electrical Force:
m

r2
3
kg  s

r12
q2

r1
 11
2
q1

r1
e
q1 q 2
1
F12  k  2 rˆ12   kq 1 q 2  
r12
r12
k 
1
4  0
;  0  8 . 854  10
 12
F
m 1-6
Gravity on Earth
• For the special case of the force near the earth
surface, the gravitational proportionality constant
is simply:
Gm e
g 
2
and the force equation reduces to:
Re


F  mg
Note: This equation assumes that the distance between the
center of earth and the object remains constant, and thus is
valid only for small altitudes.
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