tailieunhanh - Ebook Mechanical engineering systems: Part 2

(BQ) Part 2 book "Mechanical engineering systems" has contents: Introduction to kinematics, dynamics – analysis of motion due to forces, equilibrium, stress and strain, virtual work, case study - bridging gaps,. And other contents. | 4 Dynamics Summary This chapter deals with movement. In the first part the movement is considered without taking into account any forces. This is a subject called kinematics and it is important for analysing the motion of vehicles, missiles and engineering components which move backwards and forwards, by dealing with displacement, speed, velocity and acceleration. These quantities are defined when we look at uniform motion in a straight line. This subject is extended to look at the particular case of motion under the action of gravity, including trajectories. This chapter also looks at how the equations of motion in a straight line can be adapted to angular motion. Finally in the first half the subject of relative velocity is covered as this is very useful in understanding the movement of the individual components in rotating machinery. In the second part of this chapter we consider the situation where there is a resultant force or moment on a body and so it starts to move or rotate. This topic is known as dynamics and the situation is described by Newton’s laws of motion. Once moving forces are involved, we need to look at the mechanical work that is being performed and so the chapter goes on to describe work, power and efficiency. Newton’s original work in this area of dynamics was concerned with something called momentum and so this idea is also pursued here, covering the principle of conservation of momentum. The chapter extends Newton’s laws and the principle of conservation of momentum to rotary motion, and includes a brief description of d’Alembert’s principle which allows a dynamic problem to be converted into a static problem. Objectives By the end of this chapter the reader should be able to: ᭹ ᭹ ᭹ ᭹ ᭹ ᭹ ᭹ ᭹ ᭹ define displacement, speed, velocity and acceleration; use velocity–time graphs and the equations of motion to analyse linear and rotary movement; understand motion due to gravity and the formation of trajectories; calculate the velocity of one