Page 78 - CITS - WCS - Mechanical

WORKSHOP SCIENCE - CITS

EXERCISE 6 : Friction

Concept of Friction: Friction is the force that opposes motion between any surfaces that are in contact. There
are four types of friction: static, sliding, rolling, and fluid friction. Static, sliding, and rolling friction occur between
solid surfaces. Fluid friction occurs in liquids and gases.

Laws of Friction
The laws of friction are
• Friction is proportional to the normal force exerted between the surfaces.

• Friction does not depend on the area of contact.
• Friction force depends on the type of surfaces in contact.
• The coefficient of static friction is greater than the coefficient of kinetic friction.

First Law
“For any object under motion, the friction is proportional and perpendicular to normal load.”
Second Law
“The surface characteristics an object comes in contact with determines the friction between them

Third Law
“For any two objects moving across each other, the area of contact surface does not influence the Frictional force
between them.”

Fourth Law
“The kinetic friction between two dry objects is independent of the relative surface velocity.” Therefore, kinetic
friction is independent of velocity.

Fifth Law
“The coefficient of static friction is more than the coefficient of kinetic friction.”

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CITS : WCS - Mechanical - Exercise 5