March 14, 2019


The Physics of Fungos (David Kagan, March 5, 2019, Hardball Times)

Maybe you don't know what the heck a fungo is. It is a bat designed specifically to hit balls tossed upward by a hitter as opposed to balls thrown by a pitcher. For example, a coach might use a fungo to hit balls for infield practice. A sample fungo is shown below. Why would a fungo be any different than a bat used by a player in a game? That's where the physics comes in.

Think about the Home Run Derby. In about two minutes, a slugger takes roughly 25 swings. At that point, he almost always calls "time out" because he is exhausted. Now, imagine the situation of some poor coach who needs to hit fly balls to his outfielders for half an hour. A fungo bat is designed to address that and make it easy to hit pop flies or grounders with minimal effort.

Let's try to understand how this is accomplished. Perhaps you've never noticed, but it is far easier to swing a bat if you hold it on the barrel as opposed to grabbing the handle. Physics tells us that it is always easier to get an object rotating if more of its mass is closer to the center of rotation. Why then do players insist upon using the handle?

You know the answer: if batters swung using the barrel, pitchers would routinely snap off the handle of the bat. Also, when you hit something with a tool like a hammer, you want as much of the mass as possible "on the business end" as it were.

Since a fungo bat isn't designed to hit a pitched ball, it can be much thinner than a regular bat. After all, a batter facing a pitcher must change the incoming 95 mph pitch into a ball leaving the bat with a 95-mph exit velocity. That total change in the velocity is 190 mph-95 mph to bring the ball to rest momentarily on the bat plus another 95 mph to speed it back up again the other direction. However, a coach hitting a ball after an upward toss needs only to change the velocity of the ball from zero to 95 mph.

Posted by at March 14, 2019 12:14 AM