Friction NCERT Science Class 8 Chapter 12 Summary Note

Friction
The force that opposes the relative motion between two surfaces in contact, is called friction. 

Factors affecting friction
Weight of object 
Nature of surfaces in contact

More the weight of object, more the friction. 
More smooth surface experience less friction. 

Importance of friction
Friction helps in stopping object
Friction helps to write, walk, 
Friction helps in all activities
Friction produces heat. 

Harm cause by Friction
Sole of shoes wear out. 
Machine parts get wear out. 


Friction can be increased by making surfaces rough. (More rough means more interlocking between surfaces which means more friction) 
Friction can be decreased by applying lubricant on surfaces. 
Friction can be decresed by changing shape of object. 

Rolling friction
The force that oppose motion of rolling object, is rolling friction. 

Sliding friction
The force that oppose motion of sliding object, is sliding friction. 

Sliding friction is more than rolling friction. 

Fluid
Liquid and gas are called fluid. 

Drag/Fluid friction
Frictional force exerted by fluids is called fluid. 

Aeroplane have streamline shape. Because the shape reduces fluid friction. So aeroplane flies with less opposition. 





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