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# Friction class 8 Notes Science

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## CBSE Guide Friction class 8 Notes Science

CBSE guide notes are the comprehensive notes which covers the latest syllabus of CBSE and NCERT. It includes all the topics given in NCERT class 8 Science textbook. Users can download CBSE guide quick revision notes from myCBSEguide mobile app and my CBSE guide website.

## Class 8 Science notes Chapter 12 Friction

Download CBSE class 8th revision notes for chapter 12 Friction in PDF format for free. Download revision notes for Friction class 8 Notes and score high in exams. These are the Friction class 8 Notes prepared by team of expert teachers. The revision notes help you revise the whole chapter 12 in minutes. Revision notes in exam days is one of the best tips recommended by teachers during exam days.

## CBSE Class 8 Revision Notes Science Friction

Friction is a force that opposes the relative motion between two surfaces of objects in contact. The force of friction always acts in a direction opposite to that of the applied force.

Causes of Friction: Friction exists between two surfaces due to irregularities on the surfaces of the objects in contact, interlocking of micro-level irregularities of the two surfaces and ploughing of harder surfaces into smoother surfaces.

Factors That Affect Friction
•  Roughness of the surface
•  The extent to which the two surfaces press together
•  Nature of the surface

### Types of Friction:

(i)  Static Friction: When a body is at rest, the force of friction is called the static friction and is always equal and opposite to the applied force. The force of friction which acts when the body is just at the verge of sliding on the surface is called limiting friction.

(ii)  Sliding friction: The friction force which opposes the actual relative sliding motion between two contact surfaces. Sliding friction is smaller than static friction.

(iii)  Rolling Friction: The frictional force that exists between two surfaces when a body rolls over the other. Rolling friction is smaller than sliding friction.

### Effects of Friction

•  Friction produces heat.
•  Friction causes wear and tear.
•  Friction opposes motion.

•  Friction between pen and paper enables us to write on the paper.
•  Friction between our feet and the ground allows our movements like standing, walking and running.
•  Friction between the surface of the road and tyres of our vehicles allow the vehicles to move without slipping.

•  Friction causes moving objects to stop or slow down.
•  Friction produces heat causing wastage of energy in machines.
•  Friction causes wear and tear of moving parts of machinery, soles of shoes, etc.

Friction is a necessary Evil: As friction is advantageous to us it is considered as a friend but due to its disadvantages it is a foe. Depending on the circumstance, friction can be a help or a hindrance. Thus it is a necessary evil.

Increasing Friction: By pressing the surfaces together more strongly. For e.g. when brakes are applied on a bicycle or car, the brake pads press against a moving part of the wheel and the force of friction increases.

Friction can be increased by increasing the roughness of the surfaces in contact. For example, treading of shoes and tyres is done to increase friction.

Reducing Friction: Friction between the sliding surfaces of two objects can be reduced by making the surfaces in contact smooth by polishing them.

Sliding friction between the moving parts of vehicles and machinery can be reduced by using oil, grease, graphite or any other lubricant.

Rolling friction is less than sliding friction. Hence, sliding friction is replaced by rolling friction by using rollers, like ball bearings between the hub and the axles in the moving parts of machines and vehicles.

Friction is reduced by providing wheels, e.g. suitcase, school bags of kids, etc.

Aeroplanes, boats, fishes, and birds which move through fluids have bodies of special shape, called streamlined shape, so as to reduce the friction due to fluid and avoid energy loss.

## CBSE Class 8 Revision Notes and Key Points

Friction class 8 Notes Science. CBSE quick revision note for class 8 Science, Chemistry, Math’s, Biology and other subject are very helpful to revise the whole syllabus during exam days. The revision notes covers all important formulas and concepts given in the chapter. Even if you wish to have an overview of a chapter, quick revision notes are here to do if for you. These notes will certainly save your time during stressful exam days.

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