Write important points of Newton’s third law of motion.

Explanation

(i) In the law action and reaction both are force which indicate that forces are always in pair. Force applied by B on A is equal to force applied by A on B but in opposite direction
(2) Isolated force do not exist becase forces are always in pair.
(3) Action and reaction force are equal in magnitude but act on different object . thus action is cause and rection is effect.
(4) Action and rection are force which are on given pair.
by Newton third law of motion
`vec( F )_(AB) =- vec(F)_(BA)`
When we consider motion of any one object (A and B) then we have to consider force on one object only .
it is not correct consider resultant force as zero .
When we consider system to two partice A and B then `vec(F )_(AB) ` and v`ec( F)_(AB)` are internal forces of system (A and B) resultant of internal forces is zero. Hence we can use Newton second law system of particles also.