The Physics of Car Crashes—and Why You Should Avoid Them

Two cars in crash test
“It’s not the fall that kills you; it’s the sudden stop at the end.”
― Douglas Adams

That quip by famed satirist and author of the 5-book “trilogy” The Hitchhiker’s Guide to the Galaxy may be moderately funny (all right, somewhat lame), but it also happens to be literally true. The scientific basis underlying this assertion can be expressed as a two-part logical equation, where…

  • “Vi” is your initial velocity
  • “t” is the total length of time of your fall
  • “a” is acceleration due to gravity as you fall
  • “Vf” is final velocity

…and where…

  • “m” is momentum
  • “ΔV” is change in velocity
  • “ΔT” is the time it takes to stop falling
  • “F” is force

Equation for falling and stopping

The first half of the equation denotes the fall (which is not fatal); the second half denotes the sudden stop (which most assuredly will be). Put another way, it’s not gravity you have to worry about, but Force.

Hidden Figures: The Uncounted Cost
of Car Damage You DON’T See

Damaged red car

“A small hole not mended in time
will become a big hole much harder to mend.”
— Chinese Proverb

It’s an annoying scenario, and one that is all-too-familiar to many of us. You exit a store laden with groceries, only to discover that someone in the parking lot has bumped into your car with theirs, putting a long, ugly scuff mark into that once flawless finish, or perhaps shattering a headlight. To add insult to injury, they didn’t even do you the courtesy of slipping a piece of paper with their contact information behind the windshield wiper.

Or you are parked at a stoplight, patiently waiting for it to turn green, when a young, careless driver, with one eye focused on an incoming text message instead of the road in front of them, gently rams into you from behind.

Or a slick highway catches you unaware, and you go into a hair-raising spin. You manage to regain control, but not before grazing a tree with the car, causing some minor damage to the passenger-side door.

What to do?