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2D Particle Kinetics – Energy equation
(I) Workenergy theorem (WK equation) and kinetic energy:
22
11
2
2
1
1
2
KW K
m W
m
2
υ
−−
+=
⇒
0.6 m
0.9 m
Kinetic energy:
2
1
0
2
Km
=≥
associated with motion. Unit: J
Motion of the body is from position 1 to position 2
W
12
is the
total
work by all forces on the body for the entire motion from 1 to 2.
(II) Conservative force and potential energy
(1)
A conservative force,
F
c
, is a force producing work that is independent of the body’s path of
motion.
(2)
Any conservative force has a corresponding potential energy (
U
), and vice versa:
c
F
U
⇔
(3)
Definition of potential energy:
Fc
UW
Δ
=−
(4)
Potential energy is associated with position of the body.
(5)
Gravitational potential energy:
U
g
=
mgy
where
y
is the vertical position of the body measured
from an arbitrary reference with +
y
axis upward.
(6)
Elastic potential energy:
2
1
2
e
Uk
x
=
where
x
=
l
−
l
0
is the deformation in spring.
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This note was uploaded on 03/04/2009 for the course PHYS 2305 taught by Professor Tschang during the Spring '08 term at Virginia Tech.
 Spring '08
 TSChang
 Physics, Energy, Kinetic Energy, Work, WorkEnergy Theorem

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