a. Let us call the energy of motion of the center of mass of the system 2MV2, where M is the mass of the system, and V is the velocity of its center of mass. In what case does the energy of motion of the center of mass coincide with the total kinetic energy of the system?
b. Prove that the increment of the energy of motion of the center of mass is equal to the work of the total external force, if the point of application is taken at the center of mass.