PPT - Friction Class 8 Notes | EduRev

Science Class 8

Created by: Dr Manju Sen

Class 8 : PPT - Friction Class 8 Notes | EduRev

 Page 1


CHAPTER - 12 
 
FRICTION 
Page 2


CHAPTER - 12 
 
FRICTION 
1) Force of friction :- 
  Force of friction is the force which opposes the motion of an object 
over a surface. 
  The force of friction acts between the object and the surface. 
  Eg :- A ball rolling on ground gradually slows down and comes to  
           rest due to force of friction between the ball and the ground. 
           If we stop pedalling a bicycle, it gradually slows down and                
           comes to a stop due to force of friction between the wheel and  
           the road.  
 
Page 3


CHAPTER - 12 
 
FRICTION 
1) Force of friction :- 
  Force of friction is the force which opposes the motion of an object 
over a surface. 
  The force of friction acts between the object and the surface. 
  Eg :- A ball rolling on ground gradually slows down and comes to  
           rest due to force of friction between the ball and the ground. 
           If we stop pedalling a bicycle, it gradually slows down and                
           comes to a stop due to force of friction between the wheel and  
           the road.  
 
2) Factors affecting friction :- 
      Friction depends upon two factors. They are :- 
   i) Nature of the surfaces in contact. ( The smoothness of the  
      surfaces).  
  ii) How hard the surfaces press together. 
      Friction is less on a smooth surface. 
 
 
 
 
    
          
        Friction is more on a rough surface. 
 
       
         
 
Page 4


CHAPTER - 12 
 
FRICTION 
1) Force of friction :- 
  Force of friction is the force which opposes the motion of an object 
over a surface. 
  The force of friction acts between the object and the surface. 
  Eg :- A ball rolling on ground gradually slows down and comes to  
           rest due to force of friction between the ball and the ground. 
           If we stop pedalling a bicycle, it gradually slows down and                
           comes to a stop due to force of friction between the wheel and  
           the road.  
 
2) Factors affecting friction :- 
      Friction depends upon two factors. They are :- 
   i) Nature of the surfaces in contact. ( The smoothness of the  
      surfaces).  
  ii) How hard the surfaces press together. 
      Friction is less on a smooth surface. 
 
 
 
 
    
          
        Friction is more on a rough surface. 
 
       
         
 
         Friction is more if the surfaces are  
        pressed harder. 
 
 
 
                                                                    Friction is less if the surfaces are 
                                                                    not pressed harder. 
  
Page 5


CHAPTER - 12 
 
FRICTION 
1) Force of friction :- 
  Force of friction is the force which opposes the motion of an object 
over a surface. 
  The force of friction acts between the object and the surface. 
  Eg :- A ball rolling on ground gradually slows down and comes to  
           rest due to force of friction between the ball and the ground. 
           If we stop pedalling a bicycle, it gradually slows down and                
           comes to a stop due to force of friction between the wheel and  
           the road.  
 
2) Factors affecting friction :- 
      Friction depends upon two factors. They are :- 
   i) Nature of the surfaces in contact. ( The smoothness of the  
      surfaces).  
  ii) How hard the surfaces press together. 
      Friction is less on a smooth surface. 
 
 
 
 
    
          
        Friction is more on a rough surface. 
 
       
         
 
         Friction is more if the surfaces are  
        pressed harder. 
 
 
 
                                                                    Friction is less if the surfaces are 
                                                                    not pressed harder. 
  
3) Cause of friction :- 
   Friction is caused due to the interlocking of irregularities between the  
  two surfaces in contact. 
  Smooth surfaces have minute irregularities between the two surfaces.  
  Rough surfaces have larger irregularities between the two surfaces.  
  So force of friction is more if the surfaces are rough. 
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