Question

why the sum of all the external forces in a body is zero please tell me

Answer 1

~$\small \blue {\sf{Answer }}$✨❤

We know that Newton's second law is valid in an inertial frame and the law states that,

Linear momentum remains constant if net external force on the system of particles is zero.

$F \: resultant \: </p><p> </p><p> = \: dt \: / \: div \: dP</p><p>$

Hence, since F resultant =0,

we can say that momentum of system will not change with time.

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