conservation of momentum

Question

In an isolated system with internal impulsive forces, which is conserved?

RankGuru · Accepted Answer

For an isolated system (where the net external force $\vec{F}_{ext} = 0$), the **total linear momentum** is always conserved. Internal forces (like those during a collision or explosion) appear in equal and opposite pairs according to Newton's Third Law, so their net impulse on the *entire* system is zero. While internal forces can change the individual momenta of parts of the system and can change the system's kinetic energy (e.g., converting it to heat), the total $\sum \vec{p}$ remains constant.

Rank Guru

conservation of momentum

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