Suppose
you
needed
to
lift
something
,
and
there
weren't
any
simple
____________________
to
help
you
.
You
have
only
your
own
muscles
to
rely
on
to
do
work
.
The
stronger
you
were
the
____________________
it
would
be
.
If
you
were
so
strong
,
you
might
try
to
think
of
something
to
help
you
.
A
rope
passed
over
a
branch
might
help
make
the
work
easier
.
But
it
would
also
have
its
problems
reply
actions
for
instance
.
To
solve
this
problem
you
might
think
using
a
____________________
,
one
with
a
groove
on
it
mounted
,
so
it
can
turn
and
so
you
can
hang
it
from
something
.
When
a
____________________
is
passed
over
this
,
it
can
move
with
much
less
friction
and
it
can
scraping
over
a
stretch
.
The
groove
in
the
wheel
keeps
the
rope
from
slipping
off
.
The
whole
arrangement
,
the
wheel
and
the
rope
that
goes
over
it
is
called
a
____________________
.
Pulleys
are
simple
machines
that
help
people
do
work
.
This
one
is
a
fixed
pulley
because
it
stays
in
one
place
as
you
use
it
.
How
does
a
fixed
pulley
make
lifting
things
easier
?
Suppose
you
attach
a
____________________
or
a
load
here
.
Up
or
down
on
your
end
of
the
rope
causes
up
or
on
the
other
end
.
You
apply
a
____________________
in
one
place
and
that
produces
a
force
in
another
place
to
lift
the
load
.
The
amount
of
force
you
apply
is
the
same
as
the
force
that
act
on
the
load
.
If
the
load
weighs
25
____________________
then
you
have
to
pull
down
with
the
forces
25
pounds
in
order
to
lift
it
and
if
it
weighs
50
pounds
on
.
You
have
to
pull
down
with
fifty
pounds
of
force
same
amount
of
force
you
need
to
lift
the
____________________
without
the
pulley
.
So
,
affixed
pulley
does
not
increase
your
force
,
it
helps
you
left
things
by
changing
the
direction
of
force
.
It
allows
you
to
____________________
down
in
order
to
lift
something
up
,
for
instance
if
you
want
to
raise
a
flag
up
a
pole
you
don't
have
to
climb
the
pulley
and
pull
it
up
.
You
can
put
a
fix
pulley
at
the
top
and
raise
the
____________________
without
leaving
the
ground
.
And
if
you
look
the
rope
around
a
second
fixed
pulley
a
bottom
,
you
can
also
pull
the
flag
down
.
If
you
left
something
by
pulling
it
up
only
your
____________________
do
the
work
When
you
pull
down
your
own
way
can
help
you
.
Using
your
own
weight
as
a
force
you
can
raise
something
that
weighs
less
than
you
do
.
But
not
something
that
weighs
more
,
but
with
a
pulley
you
don't
have
to
use
only
your
own
weight
.
Suppose
you
want
to
lift
something
that
weighs
100
pounds
.
You
could
____________________
another
weight
,
a
counterweight
,
and
you
at
the
end
of
the
rope
.
If
the
counterweight
weighs
90
pounds
that
would
lift
the
load
but
all
you
have
to
____________________
the
difference
,
10
pounds
of
force
,
and
you
could
lift
it
.
Fixed
pulley
and
counterweights
are
often
used
in
lifting
machines
like
____________________
.
