Multi-Object Systems [!copyright and waiver^SectionEdit.png!]
The linear form of Newton's Second Law when written in terms of momentum implies that it is easily generalized to allow for a system consisting of many objects. Simply add the contributions from all the objects within the system:
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\begin
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[ \sum_
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\vec
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_
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= \sum_
\vec
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_
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+ \sum_
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\vec
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]\end
It is important to realize that although we are now allowing multiple objects within the system, the relevant impulse to add on the right hand side of Newton's Second Law is still only the external impulse. Impulses applied to one system constituent by another system constituent are canceled by Newton's Third Law.