Friction: A Necessary Evil States

Friction is a force of contact which is equally useful and harmful for daily activities. People can walk easily due to friction between the road and footwear. At the same time more friction damages engines. In this concept, the students will understand the importance of friction and know how to increase or reduce it.

After reading the concept, students will be able to:

Describe the advantages of frictional force.
State the disadvantage of frictional force.
Explain the methods of reducing friction.
Describe how the use of lubricants such as grease oil affects friction.
Answer- what is ball bearing and mention its uses.
Recite the methods of increasing friction.

Each concept is explained to class 4 students using descriptions, illustrations, and concept maps. After you go through a concept, assess your learning by solving the two printable worksheets given at the end of the page.

Download the worksheets and check your answers with the worksheet solutions for the concept Friction Is a Necessary Evil provided in PDF format.

Friction Is a Necessary Evil:

Friction is a force that comes into play when two surfaces come in contact. The frictional force has its share of both advantages and disadvantages. These are briefly described below—

Advantages of Frictional Force:

Many of our daily activities are dependent on the application of frictional force. Some of the examples are listed here.

Without frictional force, we will not be able to light a matchstick by rubbing it against a matchbox.
Friction between the feet and the ground helps us walk.
Due to frictional force, we can write with a pen on paper.
Friction between the tyres and roads helps in vehicle movement.
The construction of a building is possible because of the frictional force between the bricks.
Friction allows us to fix an iron nail on the wall.
Frictional force helps us in climbing.

Disadvantages of Frictional Force:

Although friction does help us in our day-to-day activities, it also creates various problems. Some of them are mentioned below—

Frictional force produces heat. So, machines have to overcome friction to continue their movement, thereby causing wastage of energy.
Friction causes wear and tear of objects.
Soles of shoes wear out due to friction.
Tyres of bicycles and automobiles wear out due to friction.
Knives and razors become blunt due to friction.
Friction force also decreases the speed of a moving object or sometimes stops it.
In some instances, friction can cause massive noise pollution.
When aeroplanes take off, they produce loud noise because they move against the air resistance.

Methods of Reducing Friction:

There are many ways to minimise the ill effects of frictional force.

1. Use of Lubricants:

Substances that can reduce the amount of friction and wear and tear of different objects are called lubricants.

Examples: Motor oil, gel, silicone, oil, grease, wax etc.

Grease is used in different parts of automobiles and bicycles to reduce friction and increase efficiency.

2. Polishing:

Polishing a surface can make rough surfaces smooth and reduce friction.

3. Applying Oil or Powder:

Oil is applied to the hinges of the door to reduce friction and create a smooth movement of the door.
Powder is sprinkled over a carrom board to decrease the friction between the board surface and the striker.

4. Using Rollers, Wheels and Ball Bearings:

Using rollers and wheels reduces friction. Wheels are used in vehicles to reduce friction. Rollers are used in luggage bags to reduce friction.
When an object rolls over a surface, it produces motion against the rolling friction.
The value of rolling friction is lesser than the static and sliding friction.
Due to lesser friction, objects can easily move on the surface.
In this way, all adverse effects of friction such as the production of heat and wear and tear of the mechanical parts are also reduced.
Ball bearings are used in fans and bicycles to reduce the adverse effects of friction.

Methods of Increasing Friction:

The soles of the shoes are grooved, which increases the friction between our feet and the ground, and we can walk properly.
The tyres of vehicles have treads that allow them to have a grip on the road.
Gymnasts apply chalk powder on their hands to increase their grip.
The brake pads of vehicles are coarse, so when breaks are applied, it helps the vehicle stop on the road.
Kabaddi players rub their hands with soil which increases the friction between the hands and allows them to easily grip the opponent.

Viscous Drag:

Any type of fluid, either a liquid or a gas, exerts a frictional force on the objects. It is called fluid friction.
The force acting opposite to the motion of any object moving in a fluid is called drag.

The amount of fluid frictional force on an object depends on the following factors—

The shape of the object.
The viscosity of the fluid
Speed of the object with respect to the fluid.

We can say that fluid friction exerts a minimum force on a streamlined body.
So, birds and fish have streamlined bodies that help them move swiftly through air and water, respectively.
The bodies of aeroplanes, missiles, rockets, and cars are also streamlined to reduce air resistance.
Ships also have a streamlined shape to reduce friction while moving through water.

New Words:

Tyre Tread: The part of a tyre that actually comes in contact with the road.

Viscosity: It indicates the resistance of a fluid to flow.

Did You Know?

An inclined plane always reduces the frictional force. The motion of an object reduces on an inclined plane which is why the frictional force that opposes the object’s motion also reduces.