explain various types of friction. suggest a few methods to reduce friction.
Answers
First what is friction?
=> Friction is the resistance to the movement of a body over the surface of another body..
FRICTIONAL FORCE: The force which opposes the relative motion of two surfaces of bodies in contact, is called frictional force. It is calssified into 4 types..
● SLIDING FRICTION: It is the friction which comes into play when the surface of one object moves relative to the surface of another object....
● STATIC FRICTION: It is the friction which comes into play when surface of the objects are at rest telative to each other...
● ROLLING FRICTION: When one bodyvrolls over the surfavr of another, the friction offered is called rolling friction....
● FLUID FRICTION: When bodies move through fluids, fluids exert a frictional force called fluid friction or drag...
Frictions can be reduced by,
1) Using lubricants
2) ball bearings
3) oil or grease
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There are four types of friction.
(a) Static Friction (b) Kinetic Friction (c) Rolling Friction (d) Fluid Friction
(a)Static friction:-
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Friction
Table of Content
Cause of Friction
Types of Friction
Cause and Direction of Rolling Friction
Co-Efficient of Friction
Angle of Friction
Angle of Repose
Methods of Reducing Friction
Related Resources
Frictional ForceWhenever the surface of a body slides over another, each body experiences a contact force which always opposes the relative motion between the surfaces. This contact force is called frictional force. Intermolecular interaction arising due to elastic properties of matter is the cause of frictional force.This force acts tangentially to the interface of two bodies.
Cause of Friction
Old view:-
Earlier it was thought that roughness of the two surfaces causes friction in the figure because it can be easily seen that smoother the surfaces, lesser is the friction. Interlocking of irregularities of the two surfaces causes hindrance to sliding. This, however, is not the current view.
Current view:-
The current view is a slight deviation from the old view. Earlier we thought that interlocking of irregularities of surfaces was causing friction. Now, it is though that due to irregularities, the common surface area which is in actual contact of the two surfaces, is much less than the total overall area in contact. In one experiment, it came out to be 1/10,000th of the apparent area.
Thus, while the total interactive (action and reaction) forces between the two surfaces remain the same, the pressures at the points of contact are extremely high and cause the humps to flatten out (undergoing plastic deformation) until the increased area of contact enables the upper solid to be supported. It is thought that at the points of contact, small, cold-welded joints are formed by the strong adhesive forces between molecules which are very close together. These have to be broken away before one surface can move over the other. Thus the force of friction is found to depend upon the following factors.
A Microscopic Model of Friction
(i) The nature of two surfaces with the surfaces are being pressed together.
(ii) Normal force with the surfaces are being pressed together.
(iii) Actual area of contact
Types of Friction
There are four types of friction.
(a) Static Friction (b) Kinetic Friction (c) Rolling Friction (d) Fluid Friction
(a)Static friction:-
Static Friction
Static friction is the force of friction between two surfaces so long as there is no relative motion between them. It is always equal to the applied force. The static frictional forces are incorporated in the following inequality.
The magnitude of static friction fs (static frictional force) has a maximum value fs,max that is given by,
fs,max = µsN
Here µs is the coefficient of kinetic friction and N is the normal force.
So, coefficient of static friction, µs= fs,max /N
Static friction is always equal to the apllied force. It will be observe that value of static friction increases to certain maximum value, beyond which if the applied force is increased body starts moving. This maximum value of force of friction is called limiting friction.
Limiting friction is the maximum value of force of friction between two surfaces so long as there is no relative motion between them.
(b) Kinetic friction:-
Kinetic friction is the force of friction which comes into play between two surfaces when there is some relative motion between them. The magnitude of force of kinetic friction fk (kinetic frictional force) is proportional to the normal force N.
Kinetic Friction
So,
Here µk is the coefficient of kinetic friction.
Thus, coefficient of kinetic friction, µk = fk/N