DOC.
47 293
p0V0
1
-b
E
A
C2
+
[t(L÷
(16c)
(18c)
§13. The
volume
and
pressure
of
a moving
system. Equations
of motion [75]
To
determine the
state of
the
system
under
consideration,
we
have
used
the quantities
E0,
p0,
V0,
which
are
defined with respect
to
a
reference
system
that
moves
along
with the
physical
system. However,
instead of these
quantities
we can
also
use
the
corresponding
quantities
that
are
defined with
respect
to
the
same
reference
system
as
the
momentum
G.
To
do
this,
we
must
examine
how
the
volume and
pressure
change
with the introduction of
a new
reference
system.
Let
a
body
be
at rest
with respect
to
the reference
system
S'.
Let
V'
be
its
volume with
respect
to
S',
and
V
its
volume
with
respect to
S.
It
follows
immediately from equations
(2)
that
dx.dy.dz
=
1
-
~y
j
dx'.dy'.dz'
or
r
=
J1
-
$
•
r
If
we
replace
V' by
V0
and
v by
q
in
accordance
with the
notation used,
we
will
get
'
-
JTjJ
.
(20)
To
obtain the transformation
equations
for the
pressure
forces,
we
must start
from
the transformation
equations
that
apply
to
forces in
general.
Since
we
defined the
moving
forces
in
§8
in
such
a way
that
they
can
be replaced
by
the