INTRODUCTION

A machine is a device, which is capable to do some work on application of some effort. Here, effort means input in the form of force or energy supplied to the machine to do work. The work may be explained in the form of load lifting. An illustrative example of a lifting machine is explained with Figure 13.1. Figure shows lifting of a bucket of water by applying the effort ‘P’ on one end of the rope wrapped on pulley and other end connected to the bucket of weight ‘W’.

Figure 13.1 Simple Rope and Pulley Drive

The machine can be classified as simple machine and compound machine. The machine, in which there is only one point of effort application, is known as simple lifting machine. Simple lever is an example of simple machine. The machine, in which there is more than one point for load as well as effort application, is known as compound machine. Sewing machine and compound screw jack are examples of compound machine.