The applied force is different for the two cases
The case A with a greater force involves the greatest momentum change
The case A involves the greatest force.
The initial momentum of the two ball is the same.
P = mv
where;
Since the force applied by the arm is different, the final velocity of the balls before stopping will be different.
Thus, the final momentum of each ball will be different
The impulse experienced by each ball is different since impulse is the change in momentum of the balls.
J = ΔP
The force applied by the rigid arm is greater than the force applied by the relaxed arm because the force applied by the rigid arm will cause the ball to be brought to rest faster.
Thus, we can conclude the following;
Learn more about impulse here: https://brainly.com/question/25700778