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Friction
What
is Friction?
Friction is a force which resists motion when one surface slides over
another.
It acts in a direction so as to oppose movement of surface.
Fricion exists
because surfaces are never perfectly smooth. There are irregular undulations.
When one surface slides or tends to slides over another surface, the undulations
on the two surfaces lock up. Friction arises and tends to oppose the possible
motion of the surface.
Some of the energy used to overcome friction is converted to heat and
sound.
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Is
"friction" trouble?
Friction often causes troubles. It makes the moving parts of a machine
stiff and wastes energy.
It may even cause wear in the moving parts. Friction may be reduced by
separation the contact surfaces with lubricants.
Lubricating oil is used for this purpose in joints and hinges.
An ice block slides with little friction on the table because the block
and the table are separrated by a layer of water
When a rocket
is launched, it must overcome the friction that acts between the rocket
and the air. It is alos called air resistance. The movement of the rocket
through air produces a lot of heat.
Streamlining helps to reduce air friction and the amount of heat produced.
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Is
"friction" useful?
Friction is often useful too.
It helps to stop a carwhen a force is applied to the braking systme.
When we walk we exert a force on the ground. Friction then occurs between
the ground and our shoes. It is fricion that pushes us forward.
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