Explanation of in the absence of external forces, momentum is conserved in
Answers
Law of conservation of momentum:
let us consider an isolated system .it is the system in which no external force acts .consider an isolated system of two smooth hard intracting balls.having mass m1 and m3 moving in same direction with velocity v1 and v2.
both balls collide and after collision the ball with mass m1 moves with velocity v1'and m2 with v2'.
to find cgange in momentum we use eq
f'×t=m1v1'-m1v1
for ball of mass m2 it will be
f×t=m2v2'-m2v2
Adding these both we get
(f+f')t=(m1v1'-m1v1)+(m2v2'-m2v2)
As we know the action force f is equal and opposite to reaction force f' so f=-f' .
thus on left of equation equals to zero .i.e
0=(m1v1'-m1v1)+(m2v2'-m2v2)
also written as
(m1v1+m2v2)=(m1v1'+m2v2')
means the total initial momentum of the system before collision is equal and opposite to the final momentum of the system after collision.
"the total change in momentum of the isolated system is equal to zero".
i really hope that it will help you .stay blessed☺
Because in physics, only ‘Net External Force’ can change momentum. So if it isn’t there, then there’s is no one to change momentum. And momentum stays conserved.
It is a fundamental law (Newtons’ laws of motion). And fundamental laws are to be accepted. One can just verify such laws and not prove them.
The Newton's first law of motion states, A body continues in its state of rest or of uniform motion unless acted upon by some external force. On an elementary level we can say that Conservation of momentum is required by Newton's first law of motion.
To your given situation: Your given situation is simply impossible. Both of them will never come to rest. After collision, they will move as such so that their momentum will be conserved.
Whether they both will get attached and move together or one will stop and other will move away in opposite direction will depend on ‘Coefficient of restitution’ between them.
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