momentum of whole universe remains contant. is it true/false.what is the reason

 

Answer to these types of question requires higher knowledge of physics which you will encounter in your post graduation. The conservation of momentum is applicable only in the case when there is no force acting on the system. It is possible for momentum to be conserved in one direction and not in the other. Therefore, in order for the momentum to be conserved in that one direction there should be no external forces present. If an external force acts, the system would change, and the momentum would not be conserved.

In simple words, there is no external force acting on the whole universe as there is no bigger system outside of it. Therefore, the momentum of the whole universe is conserved. Also, if something applies a force to a system, then the system, no matter how intricate, exerts an equal but opposite force on that something. And if we include that external thing as part of a new, larger system, the whole system conserves momentum. That’s why the total momentum of the universe is constant – there is no larger system containing it.