The impulse J is equal to the magnitude of the force applied to the cannonball times the time it is applied:

But the impulse is also equal to the change in momentum of the cannonball:

If we put the two equations together, we find

And since we know the magnitude of the average force and the time, we can calculate the change in momentum:
Answer:
Zero; no force is required to keep it going
Explanation:
Since the cannon ball is fired into frictionless space, there will be nothing to stop it, so it will keep going and going.
Answer:
velocity at the top: 0 m/s
acceleration at the top: -9.8 m/s²
Explanation:
Assuming up is positive and down is negative;
The velocity of the ball at the top of its path will be 0 m/s and the acceleration will be negative.
The velocity is 0 m/s because the ball does not move at the top of its path, and it switches from a positive velocity to a negative velocity. It must go through 0 in order to go from positive to negative.
The acceleration, however, is always negative no matter where the ball is in its motion. This negative acceleration causes the ball to slow down as it reaches the top, and speed up as it reaches the bottom.
<u>Think about it:</u> If there wasn't a negative acceleration, and it was instead 0, the ball would never come back down and instead keep going in a straight line.