The momentum of a system with respect to centre of mass

The rate of change of angular momentum of a system of particles about the centre of mass is equal to the sum of external torque about the centre of mass when the centre of mass is :

The rate of change of angular momentum of a system of particles about the centre of mass is equal to the sum of external torque about the centre of mass when the centre of mass is :

A rigid system consists of two point masses,A and B of masses 1kg and 2kg respectively.At an instant the kinetic energy of A with respect to the centre of mass is 2 Joules and the velocity of centre of mass is 2m/s.The kinetic energy of the system at this instant is?

Statement-1 : Total linear momentum of system in centre of mass frame is zero only when there is no net external force. Statement-2 : Total linear momentum of system is conserved in absence of net external force.

Consider the following two statements: A. linear momentum of the system remains constant. B. Centre of mass of the system remains at rest

Consider the following two statements: A. linear momentum of the system remains constant. B. Centre of mass of the system remains at rest

Consider the following two statements: A. Kinear momentum of the system remains constant. B. Centre of mass of the system remains at rest