Fundamental concept of Engineering Mechanics

The following are the fundamental concept used in the engineering mechanics

1. Force

In general force is a Push or Pull, which creates motion or tends to create motion, destroy or tends to destroys motion. In engineering mechanics force is the action of one body on another. A force tends to move a body in the direction of its action, A force is characterized by its point of application, magnitude, and direction, i.e. a force is a vector quantity.

Units of force

The following force units are frequently used.

A. Newton

The S.I unit of force is Newton and denoted by N. which may be defined as

1N = 1 kg. 1 m/s²

B. Dynes

Dyne is the C.G.S unit of force.

1 Dyne = 1 g. 1 cm/s²

One Newton force = 10² dyne

C. Pounds

The FPS unit of force is pound.

1 lbf = 1 lbm. 1ft/s²

One pound force = 4.448 N

One dyne force = 2.248 x 10_ˉ⁶ lbs

2. Space

Space is the geometrical region occupied by bodies whose positions are described by linear and angular measurement relative to coordinate systems. For three dimensional problems there are three independent coordinates are needed. For two dimensional problems only two coordinates are required.

3. Particle

A particle may be defined as a body (object) has mass but no size (neglected), such body cannot exists theoretically, but when dealing with problems involving distance considerably larger when compared to the size of the body. For example a bomber aeroplane is a particle for a gunner operating from ground. In the mathematical sense, a particle is a body whose dimensions are considered to be near zero so that it analyze as a mass concentrated at a point. A body may tread as a particle when its dimensions are irrelevant to describe its position or the action of forces applied to it. For example the size of earth is insignificant compared to the size of its orbits and therefore the earth can be modeled as a particle when studying its orbital motion. When a body is idealized as a particle, the principles of mechanics reduce to rather simplified form since the geometry of the body will not be involved in the analysis of the problem.

4. Rigid Body

A rigid body may be defined a body in which the relative positions of any two particles do not change under the action of forces means the distance between two points/particles remain same before and after applying external forces. As a result the material properties of any body that is assumed to be rigid will not have to be considered while analyzing the forces acting on the body. In most cases the actual deformations occurring in the structures, machines, mechanisms etc are relatively small and therefore the rigid body assumption is suitable for analysis