I often hear of someone’s shoes coming off in an auto accident or other traumatic injury? It must be the force of impact, but does the force always go from head to feet? Why doesn’t other clothing get blown off?
I don’t know how other pieces of clothing could come off. Things like shirts and pants take a bit of effort to get on and off, but shoes you can usually just slip off. Now just thing about them getting hooked around pedals and seat cushions.
PS I HAVE seen this happen. I was first on the scene of a really nasty motorcycle accident, I still remember seeing they bike laying on the gound with the boots still on the bike where his feet would have been. (He was about 20 feet away).
It does to passengers in planes that suffer in-air catastrophic failures, though its the result of +500MPH wind rather than momentum…
There are places on the internet where you can look at grisly accident photos, and you can see in these pictures that people’s clothing can indeed sustain damage or come off.
I recently saw a picture of a teenager who had been hit by lightning. It literally knocked him out of his shoes. His clothes had various holes and scorch marks.
Two things. One is that shoes are not connected to your body as firmly as a jacket. And two is torque. Your feet are the greatest distance from your center of mass, so you have the force times the length of that lever arm working on them.
Also, shoes are dense (their mass/volume is much more than most clothes). This means that they have a lot or inertia, so in a car crash, when the car decelerates rapidly they will tend to keep going, and slip off the foot.
At a certain speed, if a vehicle hits a pedestrian it will knock them over.
Faster, and it will knock them out of their shoes.
And if the vehicle is traveling really fast and hits a pedestrian it will literally knock them off their feet. Meaning, their feet will be sitting there on the ground, and the rest of their body will be somewhere else.
Take a look for yourself. Here is a video of a skateboarder in the X-Games falling from 50 feet. Upon impact his shoes fly off. Just a matter of them not being as secure as the rest of the clothing. Don’t worry about watching the video. Somehow he walks away from it.
Shoes are not firmly attached to bodies and they have inertia. When the body accelerates fast enough the shoes the shoes stay approximately where they were and the body goes blying.
It’s for that reason that parachute troopers wear high, laced boots. The opening of the parachute can jerk low-cut shoes off. In that case the body slows rapidly and the shoes keep going.
Normandy, June 6, 1944, 0430 hours:
“Hauptmann! A bunch of shoes just dropped out of ze sky! I think ze British are coming!”
I think the reason that paratroopers wear high, laced boots is because they are combat soldiers who are going to have to hike a jillion miles carrying 100lbs of equipment on their back after they have landed. In all my time skydiving, including some extremely hard openings (round reserve ride at terminal velocity), I have never seen or heard of anyone having their sneakers/sandals/other footwear come off due to opening shock. You’d have to be totally unlaced for that to happen.
I think that it’s a combination of things - one is the whipping effect (if you get hit and go flying through the air your feet will have a pretty high rotational speed which acts to yank your shoes off) and the other is that it’d be easy to snag a foot on something and that may rip off your shoe. A guy on a bicycle got hit in front of my house a few years ago, he came downhill very fast, driver didn’t see him and rolled into the intersection. Biker hit the front quarter panel and flew through the air (I watched him sail about 30 feet). One of his shoes was left sitting on the hood of the car.
Regarding lightning strikes, I saw a Weather Channel documentary on them and an ER surgeon with a lot of experience in that type of injury mentioned that when lightning hits you it generally travels over the outside of your body and flash-heats moisture (sweat) into steam which literally blows the clothing off your body. Since your feet tend to be pretty sweaty and confined (and possibly wet if you are standing out in the rain) that’s one reason that lightning victims are often de-shoed.
Many soldiers walk many miles through rough country and wear just plain high topped shoes. Whether or not they were really necessary, the stated reason in WWII for the boots was the one I furnished.