ELI5: How come a large, inflatable ball which weighs no more than three pounds can knock an adult man flying five feet through the air? We've all seen the videos. An inflatable ball, usually about two feet across, and full of nothing but air, hits a person at speed. Logically, the ball should bounce off harmlessly. Instead, the person gets fucking DECKED like he just ate a shotgun slug.

Why? How?