Short & Concise Friction Class 8 Notes
Firstly, let us see what we are going to study in this chapter. The overview of the chapter is very necessary for every student. This gives you an idea about the content we are going to study and can relate to our previous syllabus or chapters.
What is Friction?
What is the Force of Friction or Frictional Force?
It is the force that comes into action when the surfaces of two bodies come in contact with each other and it opposes the motion of the objects.
It is not a fundamental force.
Causes of Friction
What causes friction? Friction is caused due to the following-
- Irregularities– Due to the roughness or the irregularities present on the surfaces in contact. The surfaces get interlocked.
- Forces of attraction– Due to the presence of adhesive forces (force of attraction between the molecules of the two surfaces in contact).
Types of Frictional Force
There are mainly two types of Frictional Forces-
- Static Friction
- Kinetic Friction (Sliding Friction & Rolling Friction)
To Read More About Frictional Force Visit Here: Chapter 12 Friction
The frictional force that acts on a body when it is stationary (at rest). A body starts moving when the force applied is greater than this Static Friction.
Kinetic Friction comes to play when an object starts moving (Sliding or Rolling), it is called Kinetic Friction.
Static Friction > Kinetic Friction
Also, Static > Sliding > Rolling
When a body slides over another body, it is called sliding friction.
Example: Dragging a box on the floor.
When a body rolls over another body, the friction acting between the surfaces is called rolling friction.
Example: Wheels rolling on the road is the best example of rolling friction.
What are the Advantages and Disadvantages of Friction or Force of Friction?
Advantages of Friction
Friction is something that opposes motion and is often considered evil. But Friction also plays an important part in our daily life. There are many advantages of Frictional Force. Let us look into some Advantages of Frictional Force.
- Help us to walk on the ground
- Friction helps us to write on the notebook or board.
- Friction helps us to hold things.
- We fix the nail on the wall easily because of friction, which helps in holding the nail.
- A moving vehicle comes to rest on applying brakes due to friction.
- Due to air friction meteoroids burn up or get reduced in size before entering the earth’s atmosphere.
Methods of Increasing Friction
Since the Force of Friction plays a very important role in our day-to-day life; it is sometimes necessary to increase friction.
- By making the surface rough which is in contact
- To avoid slipping, shoes are grooved.
- To avoid slipping vehicles on the road, tires are treaded.
- By increasing the mass of the object, friction is increased.
Disadvantages of Friction
Friction has many disadvantages. The main disadvantages are that it is due to friction the efficiency of any machine is decreased. It causes wear and tear of moving parts of the machine and thus decrease its life. Now, let us discuss some disadvantages of frictional force.
- It causes wear and tear.
- Due to friction, extra energy is consumed.
- Friction also produces noise.
- Friction decreases the efficiency of a machine
- Frictional Force produces a lot of heat
- Friction decreases the life of machines
Methods of Reducing Friction
Since Friction is called evil; there are many methods of reducing friction by making the surfaces in contact smoother.
- Lubrication: Surfaces can be made smoother by using oil, grease, etc.
- Sprinkling powder like on the surface of a carom board
- Use of Ball Bearings
- Making objects streamlined
- Helping objects to roll instead of sliding
Why Friction is called a necessary evil?
Answer: As friction has many disadvantages like wear and tear of objects, loss of heat in the machines, etc. it also has advantages that play a very important part in our daily life like, help in walking, applying brakes, etc. Therefore, the Frictional Force or Friction is called a necessary evil.
What is Drag?
The opposing force (frictional) exerted by the fluids (Air or Water) on a solid object is called Drag.
- It depends on speed, the shape of the body, and the nature of the fluid.
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