Biomedical Engineering Reference
In-Depth Information
Chapter 5
Simple Machines
Detailed analysis of simple machines, such as levers, pulleys, and inclined planes,
allows us to appreciate and to respect human ingenuity. As machines, they are
projected to do work and to facilitate human action.
5.1 Objectives
To apply the principle of the lever and the equilibrium conditions for a rigid
body
To classify the levers
To investigate several systems of force in the human locomotor equipment,
identifying the existing types of levers
To analyze systems with pulleys and inclined planes which, together with levers,
constitute what are called simple machines
5.2 Simple Machines
We consider a machine as being a mechanism projected to perform a particular
task, facilitating or enabling human action. Among the machines considered simple
are levers, pulleys, and inclined planes. A mechanical analysis of levers allows us
to understand and to determine the muscle efforts which are exerted on the bones to
support or to move the resistance originated by the weights of such structures,
whether or not the additional external loads are summed. The pulleys are part of
physiotherapy equipment with properties that allow a change in the direction of
forces and to multiply the effect of actions, balancing larger forces with smaller
ones. Possibly, the inclined plane is the oldest simple machine.
