"HOW FAR CAN YOU HIT ONE?"          PAGE 6

When a 30-oz. bat traveling 70 mph strikes the 5-oz. ball traveling 90 mph in the opposite direction, they remain in contact for about 2 milliseconds. What happens? Well, we know from experience that the ball ends up sailing towards the outfield at about 100 mph. But what happened in the collision? There is a very important principle in physics called "conservation of momentum." This law states that there must be the same amount of momentum after the collision as there was before the collision. You have to add up ALL the momentum before and after. So in our case, you add up the bat + ball before, and that must equal bat + ball after. In this collision, the bat slows down and gives much of its momentum to the baseball.

So in our collision between bat and ball, what is happening? Both objects experience an equal change in momentum as a result of the collision. But the greater mass of the bat means that, for a given change in momentum, it will experience a much smaller change in velocity than the ball. The much lighter ball undergoes a large change in velocity, which results in the ball flying away towards the outfield.

It would seem, then, that a large, heavy bat would be best for hitting a ball a long way, since once a big bat is moving at a given speed it has greater momentum than a light bat. However, a large, heavy object also requires a great deal of effort to accelerate into motion from a standstill. It has LOTS of inertia. (Inertia is the tendency of a still object to remain still, and a moving object to keep moving.)

A batter has only split-seconds in which he must decide to swing and accelerate the bat to meet the ball. A heavy bat requires great strength and excellent reflexes to use, otherwise it becomes a liability. If the bat is too heavy, the pitch will pass by before the batter can hit it. Some professional hitters prefer relatively light bats, which they can accelerate and swing quickly and accurately. As Rickey Henderson indicates, you have to have perfect timing and judgment to get a hit with a heavy bat: "I use a light bat, about 32 or 34 ounces, to get some more bat speed. Bat speed can give you more distance, but it really gives you a chance to wait a little longer (before deciding to swing), to see the ball to the plate a little longer, so you can just make contact with it."

Many hitters who use lighter bats are "contact" hitters like Rickey Henderson. They specialize in carefully placed base hits, instead of "swinging for the fences." However, some light-bat hitters have managed to hit a lot of home runs. Hank Aaron, for instance, broke Babe Ruth's lifetime record of 714 home runs using a light bat. Remember, momentum has two components, velocity and mass. A hitter with quick wrists using a light bat can generate tremendous bat speed, thereby generating great momentum.