- When we throw a ball on the floor it starts moving with some velocity.
- But once it is rolled ideally no force is acting in the direction of motion and according to Newton’s first law the ball should keep on rolling but this does not happen.
- The ball stops after moving a certain distance so a force must be acting on it.
- That force is known as friction.
WHAT IS FRICTION?
Friction is defined as:
- The resistance offered by the surfaces that are in contact with each other when they move over each other.
- Friction works in the opposite direction in which the body is moving, making the body slow down.
- Friction is useful in most of these.
- Friction is also dependent on external factors.
FACTORS AFFECTING FRICTION
Following are the two factors on which friction depends:
1. On the nature of the two surfaces that are in contact
Friction is dependent on the smoothness or roughness of the two surfaces that are in contact with each other. When the surface is smooth, the friction between the two reduces as there is no much interlocking of irregularities taking place. While the surface is rough, friction increases.
2. On the force that is acting on these surfaces
When force is applied along with the irregularities, friction increases.
WHAT CAUSES FRICTION?
1. When we see any object, we can see the smooth surface but when the same object is viewed under a microscope, it can be seen that even the smooth appearing object has rough edges.
2. Tiny hills and grooves can be seen through the microscope, and they are known as irregularities of the surface.
3. So, when one object is moved over the other, these irregularities on the surface get entangled giving rise to friction.
4. The more the roughness, the more will the irregularities and greater will be the force applied.
FRCITION CAN BE REDUCED BY USING :
1. Grease, oil, powder, ball bearing, and cushion of dry air between the moving surfaces.
2. Using anti-friction alloys.
FRCITION CAN BE INCREASED BY :
1. Making a surface rough.
2. The sole of the shoes and the tyres of the vehicle are treated to increase friction.
LUBRICANTS
TYPES OF FRICTION
1. STATIC FRICTION
1. Static friction is defined as the frictional force that acts between the surfaces when they are at rest.
2. The magnitude of the static force is equal in the opposite direction when a small amount of force is applied. When the force increases, at some point maximum static friction is reached.
EXAMPLES OF STATIC FRICTION :
Following are the examples of static friction:
1. Skiing against the snow
2. Creating heat by rubbing both the hands together
3. Table lamp resting on the table
2. SLIDING FRICTION
EXAMPLES OF SLIDING FRICTION :
Following are the examples of sliding friction:
1. Sliding of the block across the floor
2. Two cards sliding against each other in a deck
3. ROLLING FRICTION
EXAMPLES OF ROLLING FRICTION :
Following are the examples of rolling friction:
1. Rolling of the log on the ground
4. FLUID FRICTION
EXAMPLES OF FLUID FRICTION :
Following are the examples of fluid friction:
1. The flow of ink in pens
2. Swimming
APPLICATIONS OF FRICTION:
1. Friction finds application when matchsticks are ignited.
2. Motion of pistons in a cylinder is an application of friction.
3. It is possible to write on books and board as there is friction between pen and the board.