# Kagan: The physics of choking up

From SABR member David Kagan at The Hardball Times on May 18, 2017:

Have you ever swung a bat by the barrel end? Go ahead. Give it a try. I’ll wait. You should notice that it is dramatically easier to swing the bat from the barrel end than the handle end. In general, it is easier to rotate an object that has more of its mass near the axis of rotation than an object that has more of its mass further from the axis.

The “rotational inertia” of an object is a measure of how hard it is to get the object to rotate. Objects that have a large rotational inertia have proportionally more of their mass farther from the axis of rotation than objects that have more of their mass closer to the axis. In other words, if you swing a bat by the barrel end, it has less rotational inertia than when you swing it by the handle end.

If batters can get the bat into the hitting zone as fast as possible, they can wait as long as possible to decide whether to swing and where to expect the ball. If that is their goal, then they should hold the bat by the barrel end. I suspect you’ve already realized that if a batter swung the bat by the barrel against a big-league fastball, the handle would snap like a twig.