Engineering Mechanics required for btech 1sy year students

Engg mechanics

1. Drawing Instruments Presented By: Dr Arpit Goyal Assistant Professor, CED Email : [email protected] Fundamentals of Mechanics

2. Learning Outcomes Understand the fundamentals of mechanics Understand the concept of idealization of mechanics Comprehend basic laws of mechanics Get familiar with basic dimensions used in mechanics 2

3. Structures 3

4. What is Mechanics? Branch of science that is concerned with state of rest or of motion of bodies that are subjected to action of forces 4

5. Classification of Mechanics 5

6. Rigid Body Mechanics Statics: Study of distribution and effect of forces on bodies which are at rest and remain at rest or bodies moving with uniform velocity and experiencing no acceleration. 6

7. Rigid Body Mechanics Dynamics: Study of motion of bodies and their correlation with the forces causing them (accelerated motion). 7

8. Mechanics: Idealizations To simplify application of the theory Pa rticle : A body with mass but with dimensions that can be neglected . Mass is concentrated at a point. Size of earth is insignificant compared to the size of its orbit. Earth can be modeled as a particle when studying its orbital motion 8

9. Mechanics: Idealizations Rigid Body : The physical bodies deform, although slightly, under the action of load and forces. But in many cases this deformation is negligibly small to affect the results. So it is assumed that body does not deform or the distance between any two points of the body does not change under action of applied force. In most cases, actual deformations occurring in structures, machines, mechanisms, etc. are relatively small, and rigid body assumption is suitable for analysis 9

10. Mechanics: Idealizations Concentrated Force : Effect of a loading which is assumed to act at a point on a body. Provided the area over which the load is applied is very small compared to the overall size of the body. Ex: Contact Force _ between a wheel and ground. ........ 40 kN 160 kN 10

11. Mechanics: Fundamental Concepts 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 event s :: basic quantity in Dynamics , ex: starting or stopping of the motion of the body. M ass : Distinguish between behaviour of two bodies under action of an identical force:: quantity of matter in a body:: measure of inertia of a body (its resistance to change in velocity) Force : represents the action of one body on anot her characterized by its magnitude, direction of its action, and its point of application Forc e i s a Vecto r quantit y . 11

12. Mechanics: Fundamental Principles Newton's Three Laws of Motion Basis of formulation of rigid body mechanics. First Law : 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. First law contains the principle of the equilibrium of forces main topic of concern in Statics V F 3 Equilibrium 12

13. Mechanics: Newton's Three Laws of Motion Second Law : A particle of mass "m" acted upon by an unbalanced force "F" experiences an acceleration "a" that has the same direction as the force and a magnitude that is directly proportional to the force. a F= ma A c c. e l e r a t e d . m o ti o n Second Law forms the basis for most of the analysis in Dynamics 13

14. Mechanics: Newton's Three Laws of Motion Third Law : The mutual forces of action and reaction between two particles are equal in magnitude, but opposite in direction forc e o f A 01 1 B - A . B force of B on A Actio n - reaction Third law is basic to our understanding of Force . Forces always occur in pairs of equal and opposite forces. 14

15. M kg m 15

16. Mechanics: Units Prefixes 16