A machine gun fires 23 g bullets horizontally at 260 m/s at a constant rate of 30 bullets/s.
(a) If the bullets embed themselves in a thick wooden door, what is the average force exerted on the door?
(b) If the bullets hit a steel door and rebound elastically (i.e., bounce straight back with the same speed that they hit the door), what is the average force exerted on the door?