Some examples:
A ring slides on but gets stuck trying to take it back off.
A kid puts his head through metal slats on a railing, but can’t pull it back through.
A girl gets her body in a clothes dryer, but can’t get back out.
If we can fit forward, shouldn’t we be able to fit backwards, too?
In: 358
Think of how a barb works on a fishing hook. Body parts aren’t perfectly equal and we’re kind of squishy but we also have bones. Makes for getting stuck pretty easy if spaces are tight.
It takes the same amount of force to get in and out, but the direction of the force on your body is different. Pushing your head through a grating, for example, you can put your whole body into pushing through so it won’t be a problem. But getting out you’re pulling your head *away* from your body, so you have to be more careful.
For divers or cave crawlers your ribs compress from your head down but trying to back up they are kinda like a parachute and are spread out and catch ending in death.
Answer is
Snap fit mechanism.google this.
You will see how we can use tools to snap fit into equipments. Its cost efficient, eliminates extra parts.
Main requirement is that – material should not be too rigid, it should be somewhat flexible. There you go. Our bodies are like that. We can put our leg, hand in some kind of gap, if our hand and that gap is creating snap fit then its very difficult to get out.
In 4th grade, one girl from classroom put pencil in her nose, and it wouldn’t come out. It was funny. It came out somehow.
In the case of the head through gratings thing, it’s because of your ears. Because of their shape and flexibility they will compress down when pushing forward through the grating, but will catch on the bars and prevent the head coming back the other way. I think the other situations are the same–people are not perfectly symmetrical, and so pushing stuff in one direction will be easier than pushing stuff in another.
Think of the head.
The chin is kinda like an arrow, and it can easily push through places, if a railing isn’t 100% rigid it will usually bend a little sideways, making the opening bigger.
On the back of the head though, you got the chin, going back out, it doesn’t push the railings sideways, it pushes them straight back, so the bend won’t make the head fit.
You also have the ears, which when going forwards will be squished against the head to make space.
When going back out though, the ears will be pushed forward, which will make them overlap with the other part of the ear occupying more space.
These two together means that it will be hard for the head to come out, so there will be some cases where its possible to go in but not out, and least not by simple pulling/pushing.
On cases like cave divers, its different but similar principles.
About the ring: our fingers aren’t the same size all day. For example my fingers grow wider when I am active or when I am warm. When I am relaxed or cold, I almost need to hold on to my ring because the fingers get smaller
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The ears flatten easily one way. It folds easily towards the back. But if you attemot to fold the ears forwards it actually juts out more increasing the width of your head ear to ear. Sometimes it is like those hand puzzles, there are specific angles and the exact way you the object entered isn’t found on its way back out.
Imagine a flexible cone on a stick, it’s easy to push it through a gap a bit smaller than the cone, because the gap is going to progressively compress the cone while pushing. But you can’t pull it back using just the stick, you would need to compress the base of the cone manually first.
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