112
DOC.
1
MECHANICS LECTURE NOTES
[p.
112]
fk

.p

i5

s
dt
v
dp
Energy Principle
dpv
_
dE
dt
dqv
dq,
dt
™+P'
dp?
dq,
dt
dp,
dt
y
18E
dqv
dE
dp,
^
\öqv
dt
dpv
dt
0
The chief
value
of these
equations
for
physics
consists in
the
fact
that
they
are
the
most
convenient
basis
for the
equations
of
statistical
mechanics.[71]
More
on
the
physical applications
of the
principle
of
least action
and the
Lagrange
equations.
p;
=
dH
dP"
n
'
=

" dt
dH
du'
We
apply
the
equations
to
reversible
changes
of
state
of the unit
mass
of
a
substance
p
=
v
P
=
pressure.
Heat
is
a
cyclic
process,
characterized
by a velocity
ii', which
we
identify
with
temperature.[72]
Then
we
have
P
=

dH
0V
I\dn
=
Hit'
dt
=
q
1

d(dJD
t ar