Dynamic Introduction 1. The subject of dynamics is the relation between the mechanical motion of a material body and the force acting on it 2 Two models of mechanics 1)A particle is a material body possessing mass, the shape and size of which can be neglected in investigating its motion Examples: When we study a satellites orbit the satellite may be regarded as a particle I. e, satellite- particle a rigid body in translation motion can al ways be treated as a particle I. e, rigid be oay particle 2)A system of particles is a collection of material points in which the position and motion of each particle of the system depends on the position and motion of all the other particles a rigid body is a special system of particles composed of a large number of particles, the distance between any two points of which remains the same during the whole motion. It is also called to be a non-deformable system 33 Introduction 1. The subject of dynamics is the relation between the mechanical motion of a material body and the force acting on it. 2. Two models of mechanics. 1) A particle is a material body possessing mass, the shape and size of which can be neglected in investigating its motion. Examples: When we study a satellite’s orbit the satellite may be regarded as a particle. I.e,satellite particle. A rigid body in translation motion can always be treated as a particle. I.e,rigid body particle. 2) A system of particles is a collection of material points in which the position and motion of each particle of the system depends on the position and motion of all the other particles. A rigid body is a special system of particles composed of a large number of particles, the distance between any two points of which remains the same during the whole motion. It is also called to be a non-deformable system