posted by Steve .
a rocket following a parabolic path through the air suddenly explodes into many pieces. what can you say about the motion of this system.
If only an external force can change the momentum of the center of mass of an object, how can the internal force of the engine accelerate a car?
-For the first one, I think that the since the center of mass changes, the pieces go off into different directions slower?
I don't know about the second one
Why do you think the momemtum of the system has changed? The cm will follow the same path, ignoring air resistance.
Remember, the explosion was NOT an external force.
On the second, the internal force of the engine is transcribed to an external force through the wheels on the pavement.