Part
3:
How
Two
Moons
Shepherd
Ring
Particles
Figure
4
shows
a
ring
interacting
with
two
moons.
The
inner
shepherd
moon
will
have
a
slightly
higher
speed
and
the
outer
shepherd
moon
will
have
a
slightly
lower
speed
than
the
ring
particles,
as
indicated
by
the
sizes
of
the
arrows
pointing
in
the
direction
of
the
moons’
orbits.
We
once
again
need
to
consider
Kepler’s
Third
Law.
Outer
shepherd
moon
-
N
S~
Stray
rlmg
&
e
Ring
>
S
-
Inner
shepherd
moon
Figure
4
].
0
Do
the
stray
ring
particles
move
faster
or
slower
than
the
outer
shepherd
moon
?
Faster
1
1
.
Do
the
stray
ring
particles
move
faster
or
slower
than
the
inner
shepherd
moon?
Slower
12
The
moons
have
a
strong
gravitational
effect
on
the
stray
ring
particles.
Draw
arrows
on
Figure
4
that
represent
the
direction
in
which
each
moon’s
gravity
will
act
on
the
stray
ring
particles
closest
to
it.
Label
these
arrows
to
distinguish
them
from
the
arrows
representing
the
speeds
of
the
moons.
1
3
.
Now,
consider
your
answers
from
the
previous
section,
and
draw
arrows
on
Figure
4
that
indicate
the
direction
each
stray
ring
particle
will
do
in
its
orbit
after
being
affected
by
the
shepherd
moon
closest
to
it.
Label
these
arrows
to
distinguish
them
from
the
arrows
representing
the
gravitational
forces.
D
