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There are advantages and disadvantages
of friction. Since friction is a resistance force that
slows down or prevents motion, it is necessary in many
applications to prevent slipping or sliding. But also,
it can be a nuisance because it can hinder motion and
cause the need for expending energy. A good compromise
is necessary to get just enough friction.
Questions you may have about friction
include:
-
How is friction necessary?
-
How is friction a nuisance?
-
What is a good compromise for using
friction?
Important uses
In some situations, friction is very
important and beneficial. There are many things that you
could not do without the force of friction.
You could not walk without the friction
between your shoes and the ground. As you try to step
forward, you push your foot backward. Friction holds
your shoe to the ground, allowing you to walk. Consider
how difficult it is to walk on slippery ice, where there
is little friction.
Writing with a pencil requires friction.
You could not hold a pencil in your hand without
friction. It would slip out when you tried to hold it to
write. The graphite pencil led would not make a mark on
the paper without friction.
A pencil eraser uses friction to rub off
mistakes written in pencil lead. Rubbing the eraser on
the lead wears out the eraser due to friction, while the
particles worn off gather up the pencil lead from the
paper.
Your car would not start moving if it
wasn't for the friction of the tires against the street.
With no friction, the tires would just spin. Likewise,
you could not stop without the friction of the brakes
and the tires.
Problems from friction
Friction can cause problems or be a
nuisance that you try to minimize.
Any time you want to move an object,
friction can make the job more difficult. Excess
friction can make it difficult to slide a box across the
floor, ride a bicycle or walk through deep snow.
An automobile would not move forward
very well unless its friction was not reduced. Oil is
needed to lubricate the engine and allow its parts to
move easily. Oil and ball bearings are also used in the
wheels, so they will turn with little friction.
In any type of vehicle--such as a car,
boat or airplane--excess friction means that extra fuel
must be used to power the vehicle. In other words, fuel
or energy is being wasted because of the friction.
Fluid friction or air resistance can
greatly reduce the gas mileage in an automobile. Cars
are streamlined to reduce friction. But driving at
highway speeds with your windows open can create enough
drag on the car to greatly reduce your gas mileage.
The Law of Conservation of Energy states
that the amount of energy remains constant. Thus, the
energy that is "lost" to friction in trying to move an
object is really turned to heat energy. The friction of
parts rubbing together creates heat.
You've seen how people will try to start
a fire by vigorously rubbing two sticks together. Or
perhaps you've seen an automobile spin its wheels so
much that the tires start to smoke. These are examples
of friction creating heat energy. Just rub your hands
together to create the same effect.
Besides the problem of losing energy to
heat, there is also the threat of a part overheating due
to friction. This can cause damage to a machine.
Any device that has moving parts can
wear out rapidly due to friction. Lubrication is used
not only to allow parts to move easier but also to
prevent them from wearing out. Some other examples of
materials wearing out due to friction include the soles
of your shoes and a pencil eraser.
Compromise
A compromise is needed between too much
friction and not enough.
For example, if you wanted to slide a
heavy box across the floor, you would want to reduce the
friction between the box and the floor, so that it would
be easy to move. Lubrication of some sort is often a way
to reduce friction.
But you would also want to increase the
friction of your shoes on the floor, so that you would
be able to get good traction and be able to push
effectively. Soles made of rubber material that include
treads can reduce slipping when walking or running.
Friction is necessary in many
applications to prevent slipping or sliding. But also,
it can be a nuisance because it can hinder motion. A
good compromise is necessary to get just enough friction
or a proper combination of frictions |
