تكملة 4 مدري 5
1.1 Introduction
The subject of statics developed very early in history because it’s principles can be formulated simply from measurements of geometry and force. Statics is the study of bodies that are at rest or move with constant velocity. We can consider statics as a special case of dynamics, in which the acceleration is zero.

1.2 Fundamental Concepts
Before we begin our study, it is important to understand the meaning of certain fundamental concepts and principles.

Length: Length is used to locate the position of a point in space and thereby describe the size of a physical system.

Time: Although the principles of statics are time independent. This quantity plays an important role in the study of dynamics.

Mass: Mass is a measure of a quantity of matter.

Force: Force is considered as a "push" or "pull" exerted by one body on another. This interaction can occur when there is direct contact between
Particle Particle has a mass, but it size can be neglected.

Rigid Body A rigid body can be considered as a combination of a large number of Particles

Newton’s first law: A particle originally at rest or moving in a straight line with constant velocity, tends to remain in this State provided the particle is not subjected to an unbalanced force (Fig.1-1).

Newton’s 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
( Fig. 1-2). If “F” is applied to a particle or mass “m”, this law may be
expressed mathematically as:
F = m . a

Newton s Law of Gravitational Attraction: Shortly after formulating his three laws of motion. Newton postulated a law governing the gravitational attraction between any two particles. Stated mathematically.