Mechanical Energy and Non-Conservative Work
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Description
[Model Hierarchy]
Page Contents |
|---|
Assumed Knowledge
Prior Models
Vocabulary
*System.
*[Internal Forces.]
*[External Forces.]
*[Conservative Forces.]
*[Non-conservative forces.]
Model Specification
Keys to Applicability
Can be applied to any system for which the work done by the [non conservative forces] is known. The non-conservative forces can be an external force on the system or an internal force as a result of the interactions between th eelemnts inside the system. It is specially useful for systems where the non-conservative work is zero. In this particular case the [mechanical energy] of the system is constant.
System Structure
Internal Constituents: One or more Point particles or [rigid objects].
Environment: External forces that do non-conservative work on the system.
Descriptors
Object Variables: Mass or moment of inertia for each object about a given axis of rotation, (mj) or (IjQ). {If the objects in the system interact with a spring then the spring constant.)
State Variables: Kinetic energy for each element of the system and the potential energy of the system. (? Or alternatively, linear speed or angular speed, (vj) or (_wj) for each object inside the system and the position of each of the objects in the system).
Interaction Variables: External non conservative forces (Fext) or, alternately, the work done by the external forces on the system.
Laws of Interaction
\begin
$ $\end
Laws of Change
\begin
$E_
= E_
+ W_
^
$ \end
where WNCi,f is the work done by the all the non-conservative forces on the system between the initial state defined by Ei and the final state defined by Ef and is give by
\begin
$ W_
^
= \int_
^
\sum \vec
^
. d\vec
$ \end