HBP- Hit By Pitch is a common abbreviation seen in every stat line in baseball. It is something that looks a lot less painful than it actually is- especially in the majors when some guys just shrug off 90+ mph fastballs. One interesting thing about getting hit by a pitch (which I have some good experience with) is the fact that there really is a wide range of pain associated with the event. There are many factors that effect the pain factor for the batter. Things such as location, pitch type, velocity (obviously) and most importantly, flight of the ball after contact, dictate how bad the experience is for the batter. Since I was young, and before I knew a lot about physics, I inherently knew to cringe every time a guy got nailed and the ball just dropped at his feet instead of whizzing by because of a deflection. Now it makes more sense... using simply the equation for momentum, one can see why HBPs that stop the pitch are more painful. When the ball is stopped in its tracks, the body is imposing a massive impulse force on the ball, totally matching the momentum of the pitch (which trust me, there's a lot of momentum). When the ball merely deflects off a batter and continues with some velocity past the player, the force exerted on the ball is less and therefore the force the ball exerted on the person was less.
This observation aside, there have recently been a push towards small, form fitting elbow guards worn by batters. In a batting stance, the guard protects the elbow that is almost hanging over the plate, so in the likely event that the batter is hit there, the energy from the ball will be dissipated through the guard, and not the elbow. Another pro of the small, form fitting guard is the fact that there is much less surface area perpendicular to the flight of the ball, which reduces direct hits, and therefore reduces the amount of force felt by the guard and elbow.
And for your viewing pleasure, here is a player charging the mound because of a fastball he caught up near the head
And if anyone needs any ideas for blog posts... I think you should go to 3:00 on this next video and analyze Jose Bautista's glasses, helmet and face as a system with Roughned Odor's fist and see if the system conserves energy.