The
frictional resistance force, demonstrated above, varies exponentially
with the number of turns around the fixed round object and
exponentially with the coefficient of friction. What that means
is that given a big enough rope and a strong enough round beam, a child
could gently lower a loaded log truck off the edge of a cliff as long
as there are enough wraps around the beam.
Just be sure that the
object you wrap around can take the force and the torque! If the
object can spin, you will just have a pulley and thereby almost no
frictional resistance to help you. Since the energy absorbed by
the frictional resistance is converted to heat, if you lower a heavy
load too quickly, you may burn or melt something.
This principle of friction is also used in the rope wrench.
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