Finding the Sweet Spot (Continued)

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 its length. 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, 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 find the center of percussion 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 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.

This activity has been adapted from The Sporting Life -a new book from the Exploratorium and published by Henry Holt and Company!


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