According to principle of conservation of energy, the total momentum of a system of masses in any direction remains constant unless acted upon by an external force in that direction. a. true b. false

The principle of conservation of energy states that energy can neither be created nor destroyed, but can be changed from one form to another. The law of inertia on the other hand states that a body remains at a state of rest or motion on a straight line unless compelled by an external force. So i think that the answer is B, which is FALSE because the question is more related to the law of inertia(Newtons first law) than to the law of conservation of energy. Hope i helped.