365839
Assertion : The centre of mass of an isolated system has always zero momentum. Reason : If centre of mass of an isolated system is at rest. It remains at rest.
1 Both Assertion and Reason are correct and Reason is the correct explanation of the Assertion.
2 Both Assertion and Reason are correct but Reason is not the correct explanation of the Assertion.
3 Assertion is correct but Reason is incorrect.
4 Assertion is incorrect but reason is correct.
Explanation:
If no external forces act on an isolated system, its total momentum remains constant. It can be zero or non zero. If the centre of mass is initially at rest, it will remain at rest. (by concept of inertia) So correct option is (4).