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Презентация была опубликована 11 месяцев назад пользователемJoshua Luhwago

1 MBEYA UNIVERSITY OF SCIENCE AND TECHNOLOGY DEPATMENT OF BUILT ENVIRONMENT ENGINEERING (BEE) UQF6 4YEARS PROGRAM CEB 1105; STRUCTURAL MECHANICS I

2 INTRODUCTION OF MECHANICS The state of rest and state of motion of the bodies under the action of different forces has engaged the attention of philosophers, mathematicians and scientists for many centuries. The branch of physical science that deal with the state of rest or the state of motion is termed as Mechanics. Starting from the analysis of rigid bodies under gravitational force and simple applied forces the mechanics has grown to the analysis of roboatics, aircrafts,space crafts under dynamic forces, atmospheric forces, temperature forces etc.

3 INTRODUCTION……… Engineers are keen to use the laws of mechanics to actual field problems. Application of laws of mechanics to field problem is termed as Engineering Mechanics. CLASSIFICATION OF ENGINEERING MECHANICS Depending upon the body to which the mechanics is applied, the engineering mechanics is classified as (a) Mechanics of Solids and (b) Mechanics of Fluids.

4 INTRODUCTION………..

5 INTRODUCTION……… Rigid Body: A body is said to be rigid, if the relative positions of any two particles do not change under the action of the forces. A rigid body does not deform under load! A combination of large number of particles in which all particles remain at a fixed distance (practically) from one another before and after applying a load. Material properties of a rigid body are not required to be considered when analyzing the forces acting on the body. In most cases, actual deformations occurring in structures, machines, mechanisms, etc. are relatively small, and rigid body assumption is suitable for analysis of structural members, mechanical components, electrical devices etc.

6 INTRODUCTION……….

8 INTRODUCTION………… Statics: deals with equilibrium of bodies under action of forces (bodies may be either at rest or move with a constant velocity).

9 INTRODUCTION……….. Dynamics: deals with motion of bodies (accelerated motion)

10 INTRODUCTION……….. Fundamental Concepts of Mechanics: Length (Space): needed to locate position of a point in space, & describe size of the physical system; Distances, Geometric Properties Time: measure of succession of events; basic quantity in Dynamics Mass: quantity of matter in a body; measure of inertia of a body (its resistance to change in velocity) Displacement: defined as the distance moved by a body/particle in the specified direction.

11 INTRODUCTION………… Velocity: the rate of change of displacement with respect to time is defined as velocity. Acceleration: is the rate of change of velocity with respect to time. Momentum: the product of mass and velocity is called momentum. Thus Momentum = Mass × velocity

12 INTRODUCTION…….. Weight; refers to the gravitational attraction of the earth on a body or quantity of mass. Its magnitude depends upon the elevation at which the mass is located Particle: A body with mass but with dimensions that can be neglected. A particle may be defined as an object which has only mass and no size. Such a body cannot exist theoretically.

13 INTRODUCTION……. Four Fundamental Quantities 1 Newton is the force required to give a mass of 1kg an acceleration of 1 m/s2

14 INTRODUCTION…… Other Quantities

15 FORCES SYSTEAM Force may be defined as any action that tends to change the state of rest or motion of a body to which it is applied. Force represents the action of one body on another; In dynamic force is defined as an action which tends to cause acceleration of the body. Action of a force is characterized by its magnitude, direction of its action, and its point of application. Force is a Vector quantity.

16 FORCES SYSTEAM…… Example; AB is a ladder kept against a wall. At point C, a person weighing 600 N is standing. The force applied by the person on the ladder has the following characters: -Magnitude is 600 N -The point of application is at C which is 2m from A along the ladder. -The line of action is vertical and the direction is downward.

17 FORCES SYSTEAM……. Representation of force Graphically a force may be represented by the segment of a straight line. Concentrated force/point load Distributed force

18 FORCES SYSTEAM….. FORCES SYSTEM When several forces act simultaneously on a body, they constitute a system of forces. Some of forces system include the following; -system of forces in space -a coplanar force system -a concurrent force system -a system of parallel forces -a collinear force system

19 FORCES SYSTEAM……

20 FORCES SYSTEAM......

21 RESOLUTION O LAWS OF MECHANICS F FORCES LAWS OF MECHANICS The following are the fundamental laws of mechanics; Newtons first law Newtons second law Newtons third law Newtons law of gravitation Law of transmissibility of forces Parallelogram law of forces and Triangle Law of Forces.

22 LAWS OF MECHANICS…… Newtons first law Everybody continues in its state of rest or of uniform motion in a straight line unless it is compelled by an external agency acting on it. OR 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. This leads to the definition of force as the external agency which changes or tends to change the state of rest or uniform linear motion of the body. First law contains the principle of the equilibrium of forces which is main topic concern in Statics

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