Page 1 - Lesson Notes - Friction a necessary evil

SAI INTERNATIONAL SCHOOL
Class 8
Lesson notes
Subject-Physics
CH-Friction
Subtopic-Friction, a Necessary Evil

Friction: A Necessary Evil
Frictional force plays an important role in our daily life. In some cases, friction is useful
and we want to keep it but in other cases friction is harmful and we wish to reduce it.
Examples:
1. Friction enables us to walk without slipping but it also causes wear and tear of our
shoes.
2. Friction enables a car to move on road without skidding but due to friction the tyres
of the car wears out gradually.
3. Friction is necessary for the working of machine but it also generates heat which
may damage the machines. Energy is required to overcome the friction which also
leads to wastage of energy.

Advantages of Friction
1. Enables Walking and Movement: Friction between our feet and the ground
allows us to walk without slipping.
2. Facilitates Writing: The friction between a pen or pencil and paper enables us
to write.
3. Essential for Vehicle Control: Friction between tires and the road surface
allows vehicles to move and stop safely.
4. Aids in Climbing and Holding Objects: Friction provides the grip needed for
climbing activities and holding objects securely.
5. Helps in Lighting a Matchstick: Striking a matchstick against a rough surface
generates enough heat through friction to ignite it.
Disadvantages of Friction
1. Causes Wear and Tear: Friction leads to the gradual wearing out of machine
parts, shoe soles, and other materials.
2. Generates Unwanted Heat: Friction produces heat in machines, which can lead
to energy loss and potential damage.
3. Reduces Efficiency: Overcoming friction requires additional energy, making
processes less efficient.
4. Leads to Noise Pollution: Friction in machinery can produce unwanted noise.