But what else happens when the batter makes contact with a pitch? What
factors besides aerodynamic drag determine how far and fast the ball
will travel? What makes one hit a home run, another a weak fly ball,
and another a hard grounder?
The first thing affecting
a hit is the angle and location of contact between the bat and the ball.
There is a perfect location for contact along the length of the bat,
which batters refer to as the "sweet spot," or "good wood." As Rickey
Henderson describes it, "The sweet spot is the middle of the barrel
of the bat. That's where you really want to hit the ball. . . .When
you hit the sweet spot, a lot of times you hit a home run, or just hit
the ball really hard." But, as Henderson explains, "you can't really
aim to hit with the sweet spot because pitchers are usually throwing
different types of pitches, which are moving around. So you're just
trying to make contact."
Scientists describe the sweet
spot as having two parts. One point is called the "center of percussion."
This is the place on the bat which, when hit by an impulse (the ball),
produces no impulsive reaction at the point of suspension (your hands
holding the bat). That is, if the ball hits the bat right at the center
of percussion, the bat won't wobble or twist in your hands. Instead,
all of the swing's power will be transferred from bat to ball.
On a standard baseball
bat, held at the base of the grip, the sweet spot is usually located
in the middle of a six-inch area around the maker's label, extending
up towards the tip of the bat. However, the location of the center of
percussion differs according to where you hold the bat. A hit outside
of the sweet spot results in vibration of the bat and a weak hit. It
can even break the bat.
But the sweet spot has another
component. Says Paul Doherty: "There's one spot on the bat that, when
the ball hits that place, it doesn't set up a sound wave in the bat,
a wave of vibration, which you feel in your hands as a buzzing sensation.
If you hit the ball at this "node of vibration," the wave
doesn't travel to your hands. Both the node and the center of percussion
combine to give the bat a sweet spot. If you hit the ball at that spot,
it doesn't vibrate or jump in your hands, so the energy of the bat goes
where it belongs--into propelling the ball."