Friction

UNIT - IV

Friction

Syllabus: The Laws of Dry Friction, Coefficients of Friction, Angles of Friction, Wedge friction, Wheel Friction, Rolling Resistance, Ladder friction.

Introduction

• In all chapters of statics, it was assumed that the surfaces in contact were smooth so that there was no force tangential to these surfaces.

• In practical situations, such ideal smooth surfaces do not exist and there exists a tangential force between two surfaces in contact.

• Whenever there is tendency for relative sliding motion or actual relative sliding motion of one contacting surface with respect to the other.

• The tangential force which is developed between the two surfaces in contact is called frictional force.

• The direction of frictional force is such that it always opposes the tendency for relative motion between two surfaces in contact.

• There are two types of friction: Dry friction (also called Coulomb friction) and fluid friction.

• Dry friction exists between two solid surfaces in contact when there is tendency for relative sliding motion between them whereas fluid friction exists between two layers of fluid for a similar situation.

• In this chapter, we will be discussing only dry friction.