CHAPTER 1: INTRODUCTION & STATICS OF PARTICLES STATICS AND DYNAMICS PDT 101/3 CHAPTER 1: INTRODUCTION & STATICS OF PARTICLES PREPARED BY: Tan Soo Jin sjtan@unimap.edu.my

CHAPTER OUTLINE Mechanics Fundamental Concepts Units of Measurement The International System of Units

What Is Mechanics? Study of what happens to a “thing” (the technical name is “BODY”) when FORCES are applied to it. Either the body or the forces can be large or small.

1.1 Mechanics Mechanics is a branch of the physical sciences that is concerned with the state of rest or motion of bodies that are subjected to the action of forces. Mechanics can be divided into 3 branches: - Rigid-body Mechanics - Deformable-body Mechanics - Fluid Mechanics Rigid-body Mechanics deals with - Statics - Dynamics

1.1 Mechanics Statics – Equilibrium of bodies * At rest * Move with constant velocity Dynamics – Accelerated motion of bodies

1.2 Fundamental Concepts Basic Quantities Length - locate the position of a point in space Mass - measure of a quantity of matter Time - succession of events Force - a “push” or “pull” exerted by one body on another In Newtonian Mechanics, space, time, and mass are absolute concepts, independent of each other. Force, however, is not independent of the other three. The force acting on a body is related to the mass of the body and the variation of its velocity with time.

1.2 Fundamental Concepts Newton’s Three Laws of Motion First Law “A particle originally at rest, or moving in a straight line with constant velocity, will remain in this state provided that the particle is not subjected to an unbalanced force”

1.2 Fundamental Concepts F = ma Newton’s Three Laws of Motion Second Law “A particle acted upon by an unbalanced force F experiences an acceleration a that has the same direction as the force and a magnitude that is directly proportional to the force” F = ma

1.2 Fundamental Concepts Newton’s Three Laws of Motion Third Law “The mutual forces of action and reaction between two particles are equal and, opposite and collinear”

1.3 Units of Measurement SI Units International System of units (worldwide recognition) SI system specifies length in meters (m), time in seconds (s) and mass in kilograms (kg) Force unit, Newton (N), is derived from F = ma

1.3 Units of Measurement

1.3 Units of Measurement At the standard location, gravitation (acceleration of an object caused by the force of gravity from another object) g = 9.806 65 m/s2 For calculations, we use g = 9.81 m/s2 Thus, W = mg (g = 9.81m/s2) Hence, a body of mass 1 kg has a weight of 9.81 N, a 2 kg body weighs 19.62 N

1.4 The International System of Units Prefixes For a very large or small numerical quantity, units can be modified by using a prefix Each represent a multiple or sub-multiple of a unit Eg: 4,000,000 N = 4000 kN (kilo-newton) = 4 MN (mega- newton) 0.005m = 5 mm (milli-meter)

1.4 The International System of Units