The Physics Lesson
(This piece appeared in an anonymously-penned column in Baltimore magazine about moral dilemmas, called “Do the Right Thing.”)
Baltimore magazine, August 1993
We passed from reminiscing about our glory days to re-enacting them, making a nuisance of ourselves at after-hours bars. Then we drove home, resenting our new, responsible lives.
As I weaved the car down Falls Road (not something I’m awfully proud of), Doug announced, “I’m getting out.” He reached through the window and pulled himself onto the roof--something he’d done plenty as a teenager, so I wasn’t worried. I kept my eyes on the road, hearing his body thump above me.
Suddenly, he flung himself onto the windshield. Hanging upside down, wagging his tongue, he banged and yelled “WEEALLLALHAHAHA!”
Because of his cockiness, I thought I might let him taste danger. I tapped the brakes. Somehow, that tap sent him crashing onto the hood and sliding, arms flailing, toward the front of the car.
Two options occurred to me. I could speed up to match his velocity or I could slam on the brakes and hope he would roll further than the car.
I slammed on the brakes.
Doug flew off the hood, disappeared from view, and then reappeared, bouncing down the road. The car stopped well short of him.
At first he didn’t move. But slowly, stomach first, he started laughing. He held out a hand for a lift up. No broken bones, but the asphalt had worn through his jeans and left red and purple road burns.
“Oh, man, I am so sorry,” I babbled.
“It's cool, man. Look, I m OK,” he said, jumping around.
Was I right to brake instead of accelerate? Evidently so.
Robert Reno, a UMBC physicist, explains. While it was theoretically possible for me to catch up with Doug, it was “not very likely.” When I tapped the brakes, Doug kept going at our original speed. He was traveling five miles per hour (44 feet per second) faster than the car. To have kept Doug on my five-foot hood, I would have had to gun the car from 25 mph back up to 30 mph in less than three-quarters of a second. Not very likely.
“I looked at those front tires and thought if you didn’t slam on those brakes right then ...” Doug told me later that night. “I knew you would, but I also knew that if you didn’t, that would be it.”
One year later, it occurs to me that he was already over the hood when I braked.
We’re still friends, but we rarely drink together now.
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