Chapter 7. Conservation of momentum (7-14)

Question

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Question

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{"title":" If the net external force on a system of objects is zero...then the total momentum of the system at the end of a time interval...","description":"Wrong","type":"incorrect","color":"#99CCFF","code":"[{\"shape\":\"poly\",\"coords\":\"82,133\"},{\"shape\":\"rect\",\"coords\":\"2,2,55,66\"}]"} {"title":"... is equal to the total momentum of the system at the beginning of that time interval.","description":"Correct!","type":"correct","color":"#ffcc00","code":"[{\"shape\":\"rect\",\"coords\":\"115,1,154,64\"},{\"shape\":\"rect\",\"coords\":\"118,11,119,13\"}]"}

Review

We now have the answer to the question “When is momentum conserved?” Equation 7-13 says that the total momentum does not change over the time interval \(\Delta{t}\) if the net external force on the system is zero. Then the left-hand side of Equation 7-13 is zero, and so there is zero difference between the final total momentum \(\vec{P}_f = \vec{p}_{Af} + \vec{p}_{Bf}\) and the initial total momentum \(\vec{P}_i = \vec{p}_{Ai} + \vec{p}_{Bi}\).