Chapter 1 [compatibility mode]

Applied Mechanics

Chapter 1Chapter 1

Introduction

What is Mechanics?

Mechanics is a branch ofscience which deals withscience which deals with�bodies at rest or motion

�under the action offorces.

Structure of Mechanics

Mechanics

Applied Mechanics(Mechanics applied to

Engg. Problem)

Mechanics of Rigid Bodies(Things that do not change

shape)

Statics Dynamics

Kinetics

(Forces which causes the motion are considered)

Kinematics

(Forces which causes the motion are not considered)

Mechanics of Deformable Bodies

(Things that do change shape)Mechanics of Fluids

Incompressible Compressible

Particle- it is an idealized body which may have negligible

mass and whose size and shape can be neglected

Matter- substances that posses weight, occupies space,

volume, apprehended by sense.

Body: the matter bounded by a closed surface is called

body.

Fundamental Concepts

body.

�It is accumulation of large number of particles

Rigid Body- if the relative distance between the particle of

the body is same before and after the application of forces.

Deformable body: if the relative distance between the

particle of the body is different(change) before and after the

application of forces.

Rigid Body

Deformable Body

Space - associated with the notion of the position of a point P

given in terms of three coordinates measured from a reference

point or origin.OR

The unlimited expanse of physical dimensions in which all

material objects are located

Time- It is a measure of duration between successive events.

Force - Represents the action of one body on another.Force - Represents the action of one body on another.

A force is characterized by its point of application, magnitude,

and direction.

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.

FPS: Foot, Pound, Second

CGS: Centimeter, Gram, and Second

MKS: Metre, Kilogram and second

SI: System International

Systems of Unit

SI: System International

PhysicalQuantity

Symbol UnitUnit

symbol

length l metre m

mass m kilogram kg

time t second s

electric current I ampere A

Fundamental Units

electric current I ampere A

thermodynamic temperature

T kelvin K

amount of substance

n mole mol

Sr. No.

Prefix Symbol ExpontialNotation

1 Exa E 1018

2 Peta P 1015

3 Tera T 1012

4 Giga G 109

5 Mega M 106

6 Kilo K 103

Prefix of SI system

6 Kilo K 10

7 Hecto h 102

8 Deka da 101

9 Deci d 10-1

10 Centi c 10-2

12 Milli m 10-3

13 Micro µ 10-6

14 Nano n 10-9

15 pico p 10-12

Derived Units

Physical Quantity

Unit Unit Symbol

Acceleration metre/second2 m/s2

Angular Velocity radian/second rad/s

Angular acceleration

radian/second2 rad/s2

Force Newton N or kgm/s2Force Newton N or kgm/s2

Moment of Force Newton metre Nm

Work, Energy Joule J or Nm

Torque Newton metre Nm

Power Watt W= J/s2

Pressure Pascal Pa = N/m2

Frequency Hertz Hz or 1/s

Scalar and Vector quantities

Fundamental Principles

Newton’s First Law: If the resultant force on a particle is zero, the

particle will remain at rest or continue to move in a straight line.

• Newton’s Second Law: A particle will have anacceleration proportional to a nonzero resultant appliedforce.

• When a force acts on an object, the object accelerates inthe direction of the force.

• If the mass of an object is held constant, increasing forcewill increase acceleration.

• If the force on an object remains constant, increasing mass• If the force on an object remains constant, increasing masswill decrease acceleration.

Newton’s Third Law: The forces of action and reaction

between two particles have the same magnitude and line of

action with opposite sense.

Newton’s Law of Gravitation: Two particles are attracted with

equal and opposite forces.

•every point mass in the universe

attracts every other point mass with a

force that is directly proportional to

the product of their masses and

inversely proportional to the square of

the distance between them.

2

R

GMgmgW == G = 6.67 x 10-11 Nm2/kg2

the distance between them.

Law of Parallelogram of Forces

If the two forces acting at a point be represented inmagnitude and direction by the two adjacent sides ofa parallelogram, then their resultant is represented inmagnitude and direction by the diagonal of theparallelogram passing through that point.

• Parallelogram Law

The magnitude of Resultant force R

Law of Triangle of forces

“If the forces acting at a point be representedin magnitude and direction by the three sidesof a triangle taken in order, they will be inequilibrium.”

Lami’s Theorem:

if three forces acting at a fixed pointare in equilibrium, each force will beproportional to the sine of the anglebetween the other two forces.”

Principle of Transmissibility

Conditions of equilibrium or motion are not affected by

transmitting a force along its line of action.

F and F’ are equivalent forces.

Draw one simple mechanism to liftthe body or water or weight.

Task

the body or water or weight.

Make the group of five students.

Thank YouThank You