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Definition of Friction
When the surface of a
body moves or tends to move over that of another, each body experiences a
frictional force. The frictional forces act along the common surface, and each
is in such a direction as to oppose the relative motion of the surfaces.
Types of Friction
1) Static
Friction:
The frictional force that opposes the force which tends to make an object want
to move (a push or a pull for example) from its resting position is called static friction.
When an external force is
applied to bodies that are in contact, even though they might not be in motion,
the static frictional force is opposing the motion of the object.
2) Kinetic
Friction:
The frictional force which exists between two adjacent surfaces which are in
motion relative to each other is usually slightly less in quantitative value than
static frictional force
between the surfaces and is called kinetic or dynamic friction.
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Rolling friction
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Sliding Friction
Causes of Friction
On a microscopic
level, even a highly polished surface has bumps and hollows. So as two objects
slides over each other, their contact surface is not smooth, but on the contrary,
very rough and jagged. Therefore, the surfaces kind of grind and drag against
each other. This is where friction comes from.
But friction is not
always a nuisance. In fact, without it, we wouldn't be able to walk, sit in a
chair, climb stairs, or use a mouse to surf the web. Everything would just keep
slipping and falling all over the place.
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