INTRODUCTIONSUB : MECHANICS OF SOLID

PREPARED BY……..ANJALI ACHARYA (130460106001)SHIVANI GAJJAR (130460106015)MANALI PATEL (130460106058)

CONTENT Introduction to mechanics Fundamental concepts Types of force Characteristics of a force Systems of forces Fundamental principles of mechanics (a) Principle of transmissibility of force (b) Principle of superposition of forces (c) Law of Gravitation (d) Law of Parallelogram of Forces

MECHANICS is the branch of science which deals with the state of rest or motion of particles and bodies under the action of forces.

In applied mechanics , the approach is to study systematically the laws of mechanics and their applications to engineering problems.

INTRODUCTION TO MECHANICS

ENGINEERING MECHANICSMechanics

(Branch of science)

Mechanics of rigid bodies(Engineering Mechanics)

Mechanics of deformable

bodies(Strength of materials)

Mechanics of fluids

Applied Mechanics(Application of mechanics to

engineering problems)

Mechanics of rigid bodies(Engineering Mechanics)

Dynamic

s(bodies in motion)

Kinetics(Study of motion of a body and forces responsible for the

motion )

Kinematics

(Study of motion of body , causes of motion are not

studied)

Statics(body a rest)

FUNDAMENTAL CONCEPTS SPACE : Space is the region in all

directions and contains everything within, e.g. Sun and stars , planets etc.

TIME : It is a measure of duration between successive events.

The S.I. unit of time is Second. One second is a fraction of 1/86400 of an

average solar day. PARTICLE : It is an assumed body which

may have negligible mass and whose size and shape can be neglected . E.g. a car moving on a road.

RIGID BODY : A body is said to be rigid if the relative distance between the particles of the body remain same before and after application of force.

DEFORMABLE BODY : A body is said to be deformable if its size and shape changes under application of external forces.

FORCE : Force is defined as an agency which changes or tends to change the state of body over which, it is applied.

The S.I. unit is measured in Newtons (N). The force can be applied through physical

contact or without any physical contact of body.

A force , when applied will (a) Either induce acceleration or

retardation or stop a moving body. (b) Move or try to move the body if, at

rest. (c) Induce deformation in body if body is

deformable.

TYPES OF FORCES(A) Gravitational force : It is the force exerted

by earth on a body.

(B) Magnetic force : The force which exists between magnetic poles is called magnetic force .

(C) Ionic force : The force by which ions attract or repel each other is called ionic force.

(D) Pull or Push : A body can be pulled or pushed by applying a force.

(E) Centripetal or Centrifugal force : When a body resolves around a point, an inward or outward force acts on a body, it is known as centripetal or centrifugal force.

(F) Hydrostatic force : When a body is submerged in water, the weight of water above the body induces the force on the surface of body, known as hydrostatic force.

(G) Frictional force : when a body is placed over a rough surface and a force is applied to slide the body over it, certain amount of applied force is utilized in overcoming the resistance offered by the surface unevenness.

This is mainly due to the interlocking of minutely projected particles at contact surface.

The force required to overcome this phenomenon is called frictional force.

CHARACTERISTICS OF A FORCE

A force is characterized by following : (a) Magnitude of force (b) Direction or line of action of force (c) Nature of force (d) Point of application of force

SYSTEMS OF FORCES When more than one forces act

together on a body, they may act in different configurations, known as force system.

The applied forces may act in a plane or out of plane, may pass through a common point or may remain parallel.

Various systems of forces are,

(a)Coplanar force system :- A force system in which all the forces act along a particular plane is called a coplanar force system.

(b)Non-coplanar force system :- A force system, in which the forces do not act along one particular plane, is called non-coplanar force system.

(c) Concurrent forces :- A force system, wherein, all the forces pass through a common point is known as concurrent force system.

(d)Non-concurrent force system :- If a system consists of number of forces which do not pass through a single point, the force system is known as non-concurrent force system.

Various types of forces

(e) Parallel force system :- In a parallel force system, all forces lies in one plane and they are parallel to each other.

Parallel force system

(f) Collinear force system :- A force system wherein forces act along a line, is known as collinear force system.

These forces may act in same direction or in opposite directions.

FUNDAMENTAL PRINCIPLES OF MECHANICS

(1) Principle of transmissibility of forces :-

A force can be replaced by another force of same magnitude and direction, which can act at any point along the direction of force.

It indicates that effect of force on body is same and is independent of point of application as long as it acts in the line of action of force.

(2) Principle of superposition of forces :-

When a body is under various loads, their combined effect on body is equal to sum of the effect of individual force.

The principle of superposition of forces is applicable in all the problems related to the Engineering Mechanics however, its applicability is limited to following conditions in case of problems related to the “Strength of Material”,

(1) The body behaves as elastic body.(2) The deformations are very small in

comparison to dimensions of body.

(3) Law of Gravitation :- “ Every particle of matter in the universe

attracts every other particle with a force that is directly proportional to the product of the masses of the particles and inversely proportional to the square of the distance between them.”

Mathematically, this translates into the force equation , the quantities are defined as :

WhereFg = The force of gravity (typically in

Newtons ) G = Gravitational constant = 6.67259 x 10-11 N* m²/kg m1 & m2 = The masses of the particles

(typically in kg) r = The straight-line distance between

the two particles(typically in meters)

(4) Law of Parallelogram of Forces :-

According to this law “ If two forces act simultaneously on a particle and are represented, in magnitude and direction, by two adjacent sides of a parallelogram then, the magnitude and direction of resultant force is represented by the diagonal of parallelogram which passes through their point of intersection”.

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