To find one of the "sweet spots" on a baseball bat, hold the bat, hanging down, loosely between your thumb and index finger, just below the knob on the bat's handle. Have a friend tap the bat gently with a hammer, starting at the fat end and moving toward the handle. (You can also do it yourself, although it's easier and more fun with a friend.) You should feel a vibration in your fingers whenever the bat is struck, except when the "node" is hit; then you'll feel nothing. You may also notice a slightly different sound when the node is struck.
When you hit a ball just right, you've hit it on one of the three "sweet spots" of the bat. One of these sweet spots relates to vibration. Whenever an object is struck, it vibrates in response. These vibrations travel in waves up and down the length of the object. At one point, called "the node," the waves always cancel each other out. If you hit the ball on the bat's node, the vibrations from the impact will cancel out, and you won't feel any stinging or shaking in your hand. Since little of the bat's energy is lost to vibrations when this spot is hit, more can go to the ball. The node sweet spot differs from the "center of percussion" sweet spot. When a ball hits the node, you don't feel any vibration in your hand. When it hits the center of percussion, your hand doesn't feel any force pushing against it.
To learn more about the center
of percussion and the sweet spot, see the Minimizing
Handle Forces activity.