What is friction & Types, coefficient of friction and law's of static , dynamic, solid, fluid friction ?
What is friction?
The friction force always act in the opposite direction movement of body. it is a relative motion occurs whenever one item travels relative towards another.
Type of friction?
1. Static friction
2. Dynamic friction a) sliding friction
b) rolling friction
c) Pivot friction
1. Static friction :- The friction force which is experienced by the body at rest condition is know as static friction.
2. Dynamic friction :- The friction force experienced by a body act motion conduction known as dynamic friction.
Dynamic friction is three types
a) sliding friction :- It is the friction experienced by a body when it slide over another body.
b) rolling friction:- It is the friction experienced between the surface which has balls or rollers interposed between them that is know as rolling friction.
c) Pivot friction:- It is the friction experienced by a body due to known he motion of rotation as in case of foot step bearings that is know as pivot friction.
It is may be classified in two types of friction:
a) Boundary friction (or greasy friction)
b) Fluid friction (or viscous friction)
a) Boundary friction (or greasy friction) :-
it is the friction experienced between the rubbing surface when the surface have a very thin layer of lubricant. the thin layer of lubricant results in less friction between them.
b) Fluid friction (or viscous friction) :-
The friction which is experienced between the rubbing surface when the surface have a thin layer of lubricant. in this case the actual surface do not come in contact so that surface will not rub against each other.
Coefficient of friction:- μ
The ratio of limiting friction to the normal reaction of a body is known as coefficient of friction
r = f/Rn
Where μs is the coefficient of static friction and μk is the coefficient of kinetic friction.
Law's of static friction :-
The force of a friction always act in a direction opposite to that in which the body moves.
The magnitude of the force of friction is exactly equal to the force which tends to body move.
The magnitude of the limiting friction bear a constant ratio to the normal reaction between two surface.
Law's of dynamic friction :-
The force of a friction always act in a direction opposite to the movement of a body.
The magnitude of kinetic friction bears constant ratio to the normal reaction between two surface but the value is slight lessor then that limiting friction.
For moderate speed the force of a friction remains constant but it decreases with increase of speed.
Law's of solid friction :-
The force of a friction always act in the opposite direction of the motion of the body.
The value of friction is independent of contact surface.
The force of friction is depend upon the material from which the contact surface is made.
Law's of fluid friction :-
The force of friction is almost independent of the load.
The force of friction reduces with the increase of the temperature of the lubricant.
The force of friction is different for different lubricants.
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