Rotating Mechanical Systems Background

Animation by Ames Bielenberg


 This page describes the development of mathematical models of rotating mechanical systems, though some translate (move back and forth) as well.  It is suggested that you read about translating mechanical systems first.  Since many of the concepts involved with rotating systems are analogous to those in translating systems, many of the discussions in these pages will be brief.

A list of the fundamental units of interest is listed below.  The next tab (above: "System Elements") gives a description of the building blocks of these system (inertia, spring and friction elements). This is followed by a description of  methods to go from a drawing of a system to a mathematical model of a system in the form of differential equations ("Mathematical Model").  Methods for solving the equation are given elsewhere.  The last section discusses topics relevant to energy storage and dissipation in these systems ("Energy Power").

This page does not discuss the solution of these equations, only the development of the equations through a physical model of the system.

Table of units

The table below lists commonly used units of measure for Rotating   mechanical systems in SI units.  More complete tables are available.

Fundamental Quantities   SI unit
Time - t second (s)
Moment of Inertia - J kilogram (kg-m²)
Angle - θ radians (rad)
Torque - τ Newton (N-m)
Energy - w Joule (J) [W-s, N-m]
Power - p Watt (W) [J/s]
Spring Constant - Kr (N-m/rad)
Friction Coefficient - Br  (N-m-s/rad)


© Copyright 2005 to 2019 Erik Cheever    This page may be freely used for educational purposes.

Erik Cheever       Department of Engineering         Swarthmore College