" Internal forces can change "

Choose the correct statement regarding a system of particles. Internal forces can change the kinetic energy of the system without changing system's momentum O Impulse can be defined as a very large force that acts for a very short time and causes finite change in momentum. Internal forces can change the potential energy of the system without changing system's momentum Internal forces can change the mechanical energy of the system without changing system's momentum.

Choose correct statement (A) The position of centre of mass of a system is dependent on the choice of coordinate system. (B) Newton's second law of motion is applicable to the centre of mass of the system (C) Internal forces can not change the state of centre of mass (D) Internal forces can change the state of centre of mass.

If only an external force can change the momentum of the centre of mass of an object, how can be internal force of an engine accelerate a car?