Superman leaps in front of Lois Lane to save her from a volley of bullets. In a 1 minute interval, an automatic weapon fires 146 bullets, each of mass 8.0 g, at 440 m/s. The bullets strike his mighty chest, which has an area of 0.72 m2. Find the average force exerted on Superman's chest if the bullets bounce back after an elastic, head-on collision.

In the elastic collisions, the Δv is 880 m/sec.

The total mass of the 146 bullets is 1168 grams (1.168 kg), so the total momentum transferred is 1.168 kg * 880 m/sec = 1028 N-sec/min.  Dividing by 60 sec/min, the average force is 17.1 N.