Velocity and Acceleration in Mechanisms

Chapter: 2

Velocity and Acceleration in Mechanisms

Learning Objectives

• While reading and after studying this chapter, you will be able to:

• Understand the various methods used for finding out velocity and acceleration of a given mechanism

• Explain the relative velocity method to find the velocity and acceleration of various mechanisms.

• Define the term rubbing velocity at a pin joint.

• Understand the concept of coincident point and the Coriolis component of acceleration.

• Apply the instantaneous centre method to find the velocity of various mechanisms.

• Describe the angular velocity theorem and the Kennedy's theorem.

• Apply the analytical method for finding velocity and acceleration of a single slider-crank chain.

SYLLABUS

Kinematic analysis - Velocity analysis by relative velocity method - Rubbing velocity - Acceleration analysis by relative acceleration method - Coriolis component of acceleration - Velocity analysis by instantaneous centre method -Analytical method for velocity and acceleration of slider - crank mechanism.

INTRODUCTION

• As we have discussed already, the subject theory of machines deals with the motion and forces acting on the parts of a machine.

• Since the dynamic forces are functions of accelerations (⸪ F = ma) and accelerations are functions of velocities ( ⸪ a = dv/dt), therefore the determination of velocity and acceleration of various links becomes very important in the design of any mechanism.

• The determination of motion characteristics (also known as kinematic quantities) such as displacement, velocity and acceleration of various links for a given input motion is known as kinematiç analysis.

In this chapter, we shall discuss the velocity and acceleration analysis of various mechanisms.