If the resultant of all the external forces acting on a system of particles is zero, then from an inertial frame, one can surely say that [2009]

Question

If the resultant of all the external forces acting on a system of particles is zero, then from an inertial frame, one can surely say that [2009]

Smart Achievers · Accepted Answer

(1)

$Given \sum {\vec{F}}_{ext} = 0$

$\sum {\vec{F}}_{ext} = \frac{d {\vec{p}}_{system}}{d t} = 0 \Rightarrow {\vec{p}}_{system} = constant$

i.e., Linear momentum of the system does not change in time.

Due to internal forces acting in the system, the kinetic and potential energy may change with time.

Also zero external force may create a torque. Thus the torque will change the angular momentum of the system in time.

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