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Friction Class 8 PPT

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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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FAQs on Friction Class 8 PPT

1. What is friction?
Ans. Friction is the force that opposes the relative motion between two surfaces in contact. It is caused by the irregularities present on the surfaces that come in contact with each other.
2. What are the types of friction?
Ans. There are four types of friction- static friction, sliding friction, rolling friction, and fluid friction. Static friction occurs when an object is at rest. Sliding friction happens when an object slides over another surface. Rolling friction is the force that resists the motion of a rolling object. Fluid friction occurs when an object moves through a fluid, such as air or water.
3. What are the factors that affect friction?
Ans. The factors that affect friction are- the nature of the surfaces in contact, the force pressing the surfaces together, and the relative speed at which the surfaces move over each other.
4. What are the advantages and disadvantages of friction?
Ans. The advantages of friction are- it helps in walking and running, it enables vehicles to move on the roads, it helps us to write on paper, and it allows us to hold objects. The disadvantages of friction are- it causes wear and tear of the surfaces in contact, it reduces the efficiency of machines, and it generates heat, which can be harmful.
5. How can we reduce friction?
Ans. We can reduce friction by using lubricants such as oil and grease, using smoother surfaces, using ball bearings, and reducing the force pressing the surfaces together.
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