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According to Newton's third law, two interacting objects exert equal and opposite forces on each other. And, according to one form of Newton's second law, the net force on an object is equal to the rate of change of the object's momentum. As a consequence of these two laws, the total momentum of a system of interacting objects is conserved if there is no unbalanced force from outside the system.

Sections:
00:00 - Intro
00:36 - Why is momentum conserved?
05:34 - Money analogy
07:56 - Calculating recoil momentum of a canon

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