Saturday Science: Batty for Baseball
When you live in America, it’s hard to avoid baseball. It is our nation’s pastime, after all. It’s rare to find someone who’s never swung a bat, even if it was just a whiffle-ball bat. There’s something truly satisfying about a good, solid hit: the crack that sounds when the bat hits the ball, the sight of the ball flying through the air, and the momentary sensation of contact before you drop the bat and run for first base.
Believe it or not, there’s some serious science behind the best way to hit a baseball. You’ve got physics and geometry involved in the angle you hit it, the spin of the ball as it moves through the air, the speed of the ball coming off the bat, and all sorts of stuff. Today’s focus is going to be a little smaller though: instead of measuring flight angles to determine the optimum swing motion for a given pitch at a given speed (that would be exhausting) we are simply going to experiment with a bat to find the best spot along its length to hit a ball. That spot is called the “node.”
- A baseball bat (metal or wood)
- A hammer
- A lab assistant
- Hold your bat by the handle hanging down. Don’t grip it tightly; just hang it loosely between your thumb and forefinger so it has a bit of swing to it.
- Have your lab assistant use the hammer to gently tap on the bat, starting at the bottom and slowly working their way up.
- As your assistant is tapping, pay attention to the different things you feel in your hand. You’ll feel some vibrations from some taps, and from other taps…Nothing. Or almost nothing. What’s going on here?
- Have your assistant keep tapping up and down the bat until you can figure out where they need to hit for you to feel the least vibration. When you’ve found it, you’ve found the node.
If you’ve ever played baseball, you know that sometimes when your bat connects with the ball, it sends a painful vibration into your hands. When that happens, it means the ball hit the bat somewhere other than the node.
The node is probably somewhat closer to the fat end of the bat than the handle. It occupies a special place in the physical structure of the bat. See, any time bat hits ball, the energy of the ball’s motion is transferred into the bat and causes it to vibrate. If you hit too far up or down the bat, those vibrations travel up and down the bat simultaneously, and when they hit your hand they can really hurt! But when the ball hits the node, the vibrations moving up the bat and the vibrations moving down the bat are exactly opposite each other, so they cancel each other out. The energy is still being transferred, but because you hit in the node, you can’t feel it.
In addition to saving your hands' unnecessary wear and tear, this means that there’s more energy available to bounce back into the ball and send it rocketing into the left field bleachers. See, when you miss the node, some of the energy in the vibrations goes into your hands and even into the air around the bat. When you hit the node, none of the energy is wasted getting transferred into your hands or the air, which means there’s more left over to transfer back into the ball. More energy = more force = faster, further ball.
And the principle doesn’t just apply to baseball. If a sport involves a tool hitting something (tennis racket, golf club, hockey stick, etc.) that tool has a node. Hit a slapshot too close to the heel of your stick, or hit the tennis ball right at the top edge of your racket? You’ll feel those same vibrations. If you have some other sports equipment handy, see if you can figure out a way to test for its node, too.