Final answer:
Momentum is conserved for the cannon-cannonball system as a whole when there are no external forces acting on the system.
Step-by-step explanation:
The conservation of momentum principle states that momentum is conserved in a closed system when there is no net external force acting on the system. In the case of a cannonball being fired from a cannon, the cannon and cannonball can be considered as a system. If we define the system to include the cannon and the cannonball, and assume there are no external forces acting on this system, then momentum is conserved for the system as a whole.
For example, when the cannonball is fired, it gains momentum in one direction due to the expulsion of gases in the opposite direction. The momentum gained by the cannonball is equal in magnitude and opposite in direction to the momentum gained by the cannon. Therefore, the momentum of the cannon-cannonball system is conserved.
True