A- From a rifle of mass 4 kg, a bullet of mass 50 g is fired with an initial velocity of 35 m/s. Calculate the initial recoil velocity of the rifle. B- A ball of mass 200 g travelling at 10 m/s/ is struck, by a stick so as to return it along its original path with a velocity at 5 m/s. Calculate the change of momentum occurred in the motion of the ball by the force applied by the stick