Engineering Applications

8Simple Machines

A machine can be defined as a device that makes work easier by converting energy form one form to another form, that is, it utilizes the energy received to do some useful work.

A simple machine can be defined as a mechanical device that modifies the direction and magnitude of a force or effort and makes work easier. A simple machine has no moving (or a few) moving parts, and uses a small amount of force over distance (by changing the magnitude, speed, or direction of force) to overcome larger resistance, thus making work easier by using less mechanical effort for moving an object.

There are generally accepted (defined) five classical simple machines namely the:

1. (a) Lever
2. (b) Inclined plane
3. (c) Screw and wedge
4. (d) Pulley
5. (e) Wheel and axle.

The above simple machines are generally used to lift loads hence they are also called simple lifting machines. When a set of simple machines are working together this is named a compound machine. If a simple machine does not dissipate energy, the machine energy is conserved, as it has 100% efficiency, and it is called an ideal machine.

The idea of a simple machine was introduced in the third century BC by the Greek mathematician, scientist and philosopher Archimedes of Syracuse. His remark “give me a place to stand on, and I will move the Earth,” relates to the idea of the mechanical advantage of a lever.

8.1 Load and Effort, Mechanical Advantage, Velocity Ratio and Efficiency of a Simple Machine

8.1.1 Load and Effort ...