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The

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Law of Change    Image Added

Because of the extreme restrictions placed on the systems and interactions described by the One-Dimensional Motion with Constant Velocity model, the Law of Change for the model is rather simple. The mathematical definition of velocity (for one-dimensional motion) is:

Latex
 of Change    [!copyright and waiver^SectionEdit.png!|Motion with Constant Velocity (Laws of Change)]

Because of the extreme restrictions placed on the [systems|system] and [interactions|interaction] described by the [One-Dimensional Motion with Constant Velocity|1-D Motion (Constant Velocity)] [model], the [Law of Change] for the model is rather simple.  The mathematical definition of [velocity] (for one-dimensional motion) is:

{latex}\begin{large}\[ v \equiv \frac{dx}{dt}\]\end{large}{latex}

If _v_ is a constant, this equation can be straightforwardly integrated:

{latex}

If v is a constant, this equation can be straightforwardly integrated:

Latex
\begin{large}\[ \int_{t_{aA}}^{t_{bB}} v\:dt = \int_{x_{aA}}^{x_{bB}} dx \]\end{large}{latex}

which

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(after

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algebraic

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rearrangement)

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gives:

{
Latex
}\begin{large}\[ x_{bB} = x_{aA} + v(t_{bB} - t_{aA})\]\end{large}{latex}

where:

{
Latex
}\begin{large}\[ x_{aA} \equiv x(t_{aA}) \]\[x_{bB} \equiv x(t_{bB})\]\end{large}{latex}

{note}It is rare for physics problems to specify an initial time for a motion, but rather they will usually specify an _elapsed_ time.  For instance, instead of saying "a car began a trip at 10:05 AM and drove until 10:15 AM", the problem will usually specify only that the car drove "for 10 minutes".  Elapsed time is equivalent to the difference {_}t{~}b{~}{_} - {_}t{~}a{~}{_}.{note}


Note

It is rare for physics problems to specify an initial time for a motion, but rather they will usually specify an elapsed time. For instance, instead of saying "a car began a trip at 10:05 AM and drove until 10:15 AM", the problem will usually specify only that the car drove "for 10 minutes". Elapsed time is equivalent to the difference tB - tA.