ENGINEERING MECHANICS TEXTBOOK BY CIVILENGGFORALL FREE DOWNLOAD PDF

TOPICS COVERED

Introduction to Engineering Mechanics
Composition and Resolution of Forces
Moments and their Applications
Parallel Forces and Couples
Equilibrium of Forces
Centre of Gravity
Moment of Inertia
Principles of Friction
Applications of Friction
Principles of Lifting Machines
Simple Lifting Machines
Support Reactions
Analysis of Perfect Frames (Analytical Method)
Analysis of Perfect Frames (Graphical Method)
Equilibrium of Strings
Virtual Work
Linear Motion
Motion under Variable Acceleration
Relative Velocity
Projectiles
Motion of Rotation
Combined Motion of Rotation and Translation
Simple Harmonic Motion
Laws of Motion
Motion of Connected Bodies
Helical Springs and Pendulums
Collision of Elastic Bodies
Motion along a Circular Path
Balancing of Rotating Masses
Work, Power and Energy
Kinetics of the Motion of Rotation
Motion of Vehicles
Transmission of Power by Belts and Ropes
Transmission of Power by Gear Trains
Hydrostatics
Equilibrium of Floating Bodies

WHAT EXACTLY IS ENGINEERING MECHANICS?

The subject of Engineering Mechanics is that branch of Applied Science, which deals with the laws and principles of Mechanics, along with their applications to engineering problems. As a matter of fact, knowledge of Engineering Mechanics is very essential for an engineer in planning, designing and construction of his various types of structures and machines. In order to take up his job more skilfully, an engineer must pursue the study of Engineering Mechanics in a most systematic and scientific manner.

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DIVISIONS OF ENGINEERING MECHANICS

The subject of Engineering Mechanics may be divided into the following two main groups: 1. Statics, and 2. Dynamics.

STATICS

It is that branch of Engineering Mechanics, which deals with the forces and their effects, while acting upon the bodies at rest.

DYNAMICS

It is that branch of Engineering Mechanics, which deals with the forces and their effects, while acting upon the bodies in motion. The subject of Dynamics may be further sub-divided into the following two branches – 1. Kinetics, and 2. Kinematics.

KINETICS

It is the branch of Dynamics, which deals with the bodies in motion due to the application of forces.

KINEMATICS

It is that branch of Dynamics, which deals with the bodies in motion, without any reference to the forces which are responsible for the motion.

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EFFECTS OF A FORCE

A force may produce the following effects in a body, on which it acts :

It may change the motion of a body. i.e. if a body is at rest, the force may set it in motion. And if the body is already in motion, the force may accelerate it.
It may retard the motion of a body.
It may retard the forces, already acting on a body, thus bringing it to rest or in equilibrium.
It may give rise to the internal stresses in the body, on which it acts.

CHARACTERISTICS OF A FORCE

In order to determine the effects of a force, acting on a body, we must know the following characteristics of a force :

Magnitude of the force (i.e., 100 N, 50 N, 20 kN, 5 kN, etc.)
The direction of the line, along which the force acts (i.e., along OX, OY, at 30° North of East etc.). It is also known as line of action of the force.
Nature of the force (i.e., whether the force is push or pull). This is denoted by placing an arrow head on the line of action of the force.
The point at which (or through which) the force acts on the body.

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SYSTEM OF FORCES

When two or more forces act on a body, they are called to form a system of forces. Following systems of forces are important from the subject point of view :

1. Coplanar forces – The forces, whose lines of action lie on the same plane, are known as coplanar forces.

2. Collinear forces – The forces, whose lines of action lie on the same line, are known as collinear forces.

3. Concurrent forces – The forces, which meet at one point, are known as concurrent forces. The concurrent forces may or may not be collinear.

4. Coplanar concurrent forces – The forces, which meet at one point and their lines of action also lie on the same plane, are known as coplanar concurrent forces.

5. Coplanar non-concurrent forces – The forces, which do not meet at one point, but their lines of action lie on the same plane, are known as coplanar non-concurrent forces.

6. Non-coplanar concurrent forces – The forces, which meet at one point, but their lines of action do not lie on the same plane, are known as non-coplanar concurrent forces.

7. Non-coplanar non-concurrent forces – The forces, which do not meet at one point and their lines of action do not lie on the same plane, are called non-coplanar non-concurrent forces.

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LAWS FOR THE RESULTANT FORCE

The resultant force, of a given system of forces, may also be found out by the following laws :

1. Triangle law of forces. 2. Polygon law of forces.

TRIANGLE LAW OF FORCES

It states, “If two forces acting simultaneously on a particle, be represented in magnitude and direction by the two sides of a triangle, taken in order ; their resultant may be represented in magnitude and direction by the third side of the triangle, taken in opposite order.”

POLYGON LAW OF FORCES

It is an extension of Triangle Law of Forces for more than two forces, which states, “If a number of forces acting simultaneously on a particle, be represented in magnitude and direction, by the sides of a polygon taken in order ; then the resultant of all these forces may be represented, in magnitude and direction, by the closing side of the polygon, taken in opposite order.”

MOMENT OF A FORCE

It is the turning effect produced by a force, on the body, on which it acts. The moment of a force is equal to the product of the force and the perpendicular distance of the point, about which the moment is required and the line of action of the force

Mathematically, moment, M = P × l
where P = Force acting on the body,
l = Perpendicular distance between the point, about which the moment is required and the line of action of the force.