Weird Science

# The Physics Of Getting Hit In The Face By A Baseball

Everything about the physics of a baseball and the physics of your face suggest they make a rotten pair.

by Joshua A. Krisch
Updated:
Originally Published:

A toddler was rushed to the hospital last week after a foul ball slammed into her face at Yankee Stadium. The incident made headlines because of the severity of the young fan’s injuries, but was not unique. Each year, approximately 1,700 fans are injured by foul balls and broken bats at baseball games, and this little girl was at least the third person to be injured at Yankee Stadium. The incident has renewed calls for stadiums to extend their protective netting. Teams are starting to do so, a smart move that will inevitably inspire a backlash. Before we get there, it’s helpful to understand what it means to get hit by a baseball.

What exactly happens when a leather bullet flies off a bat and onto your face? Why are these objects so dangerous, and what are they doing to the thousands of people they impact? These are not ineffable or even confounding questions. There are answers.

First, Some Physics

Major League baseballs have an average mass of 0.32 lbs (or 0.1451496 kg), Popular Mechanics assures us, and leave the bat at 110 MPH (or 49.17 m/s). Believe it or not, that’s about all the information we need to estimate the kinetic energy of a baseball as it careens toward your unsuspecting face. Kinetic energy, you may recall from high school physics class, is equal to ½ of the mass of the object, multiplied by its velocity (for our purposes, we can use the weight of the ball as the mass and the speed of the ball as the velocity). That gives us about 175 joules of kinetic energy, or about the same as a Fiat 500 traveling at one mile per hour.

Newton’s First Law of Motion tells us that, for an object like a baseball (or a Fiat, or a bullet) to come to a stop, it needs to give up all of its energy to another object. In other words, if a ball screams off a bat, hits you in the face, and stops, your face just absorbed 175 joules of energy.

Now, getting mowed down by a one-mile-per-hour Fiat may be humiliating but it doesn’t sound so bad. What makes getting hit in the face by a baseball so much more traumatic is that the contact area — your face — is small, and so is the baseball. This means that, when you take a line drive in the face, all 175 joules of energy are absorbed into a single, ball-shaped spot. In some ways this can be even more traumatic than being hit by a car, because a large part of your body absorbs a vehicular collision. Here, there’s nothing but your face to bear the brunt of it.

The same principles explain why bullets are so good at killing. They’re small and lightweight, but they move at incredible velocity and force one small area of tissue to absorb all of their energy.

Why You Really Don’t Want To Get Hit In The Face

All of the above applies whenever you’re hit by a baseball. But when you get hit in the face, like that little girl in Yankee Stadium, the negative effects multiply. First of all, your face is full of what is known as solid dense tissue — there’s a whole lot of bone in your face, and not a whole lot of water-dense organs (liver, muscle) or air-dense organs (lungs, intestines). That’s bad news when a baseball strikes (or fouls, as it were) because the denser a tissue is, the greater the number of particles hit by a moving object and the greater amount of energy exchanged. And there’s also the issue of stopping distance — since the tissue in your face is dense, there’s almost no “give”. The ball stops immediately. The difference in damage is akin to the difference between ramming your car into a mountain of pillows and a brick wall. With the brick wall, your car discharges all of its energy at once. With the pillows, it discharges it bit by bit.

Also, your face sits right in front of a pretty important organ — your brain. When something hits your face, the bone in your face compresses, and that’s where the bruises and fractures come in. But then, after the skull stops moving in response to the ball’s energy, the brain continues moving in the same direction and compresses against the skull. At high speeds, as in vehicle crashes, this can cause the brain tissue and blood vessels to stretch or even hemorrhage.

So when a baseball hits you in the face, the injury starts as a simple smack to your facial bone but can quickly progress into outright brain trauma. And that’s not the only complication.

What Sort Of Injuries Doctors Are Seeing

Your face is not only a shield in front of your brain, nor is it a mere brick wall that absorbs joules of misplaced homerun energy. It’s also where you keep your eyes, sinuses, and mouth. The American Academy of Otolaryngology says that, when a ball hits your upper face, it can fracture the delicate bones around the sinuses and eye sockets, sometimes resulting in vision loss. When the ball hits your lower face, it may change how your jaw is situated or break your teeth. Nasal injuries can be among the most serious, especially if they result in breathing difficulties.

So how can we hope to protect ourselves and our children? Step one is demanding higher safety standards at baseball stadiums or, at the very least, choosing a seat behind protective netting. When tragedy does strike, however, the most important thing is seeking immediate medical attention, the AAO writes. “When an accident happens, it’s your response that can make the difference between a temporary inconvenience and permanent injury.”