Friction
When a force acting in the opposite direction to the motion
of the body is called force of friction or friction. It is divided mainly in
two types-
Here, one is Static friction and another is dynamic
friction.
So, application which experienced by a body when at rest, is
known as static friction.
For other one, when the friction experienced by a body in
motion is called dynamic friction. It is also known as kinetic friction. It is
of the following two types-
The first one is sliding friction and another one is rolling
friction.
So, the friction which is experienced by the body, when is
slide over another body is known as sliding friction.
Therefore, the friction experienced by a body, when balls or
rollers are interposed between two surface is known as rolling friction.
Limiting friction
The maximum value of frictional force which come into play
when a body just begin to slide over the surface of the other body is known as
limiting friction.
The laws of static friction
Those are the following laws of static friction-
1.When the force of friction always acts in a direction,
opposite to that in which the body tends to move.
2. The magnitude of force of friction is exactly equal to
the force which change the body to move.
3. The magnitude of the limiting force bears a constant
ratio to normal reaction between the two surfaces.
4. The force of friction depends upon the roughness of the
surface.
5. The force of friction is independent of the area of
contact with the two surfaces.
The laws of dynamic or kinetic friction
These are the following laws of dynamic or kinetic friction-
1. The force of friction always acts in a direction,
opposite to that in which the body tends to move.
2. The magnitude of the kinetic friction bears a constant
ratio to the normal reaction between the two surface.
3. The force of friction remains constant for moderate
speeds.But it decrease slightly with the increase of speed.
Coefficient of Friction
The ratio of limiting friction(F) to the normal friction(Rn)
between the two bodies is called coefficient of friction. It is generally
donated by μ.
Mathematically, μ
= F/Rn
Limiting angle of friction
It is defined as the angle which the resultant reaction(R)
make with the normal reaction(Rn).
In the limiting case when the body just begins to Move. It
is equilibrium under the action of the following three forces-
a. Weight of the body.
b. Applied horizontal force.
c. Reaction between the body.
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