Does sliding into a base make you reach base faster?
YES! Sliding into first base (or any base for that matter) most definately gets you to the base faster (to an extent). There is a break point when sliding goes from getting you there faster, and getting you there slower, and this break point is the same time it would take you to get to the bag if you were to run right through it. Basically, two seperate physics principles will act in conjuction with one another. The first is conservation of momentum. If you are sprinting at some velocity, then your center of mass also has that velocity. When you begin to rotate your body horizontally in preparation to slide, your center of mass REMAINS at that same velocity. What does this mean? This means that now, you are going the same speed, but you have 3 or more extra feet of reach in front of you, and thus WILL reach the bag faster. There is, however, the other physics principle that will ruin this entire effect: friction. If you were to dive to early, your body would be slowed down tremendously by friction between the ground and yourself, and the extra gain in reach would make no difference when compared to the extreme loss of speed. Therefore, the best slide (to get to the base the fastest) would not be a slide at all, but rather, a dive, where your entire body is completely horizontal and airborne until the moment your front fingers touch the bag, upon which it will make no difference whether you hit the ground and begin to slow down.
Please people, this is really quite an easy thing to see if you just use your heads. Why would position players dive for plays if it didn't get them to the ball faster? You never see a third baseman try to sprint after a screamer down the line; he will always dive. Outfielders dive when they need that extra reach, which essentially gets their glove to the ball faster. IT'S SIMPLE PHYSICS!
Don't listen to all the baseball coaches and players you hear from about this argument. Chances are that they are talking from an experience perspective, rather than a scientific perspective. It's not like they could actually tell if, while they were running, they got to the bag faster from running through or sliding. Trust the science. It's never wrong.