Eli5 how can insects survive a slap from humans, a creature that’s gigantic compared to them
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There’s a few reasons, others here are mostly focusing on how the fly survives a big force. I’ll focus on why the force isn’t that big to begin with.
You’re not transferring that much momentum to the insect if you think about it (or calculate it).
If you slap a bowling ball, your hand slows down by a lot, i.e. you transferres much momentum to the bowling ball. But a fly doesn’t really slow down your hand at all.
Momentum is mass times velocity. Force is mass times acceleration, i.e. how long it takes the fly to reach it’s end velocity. Your hand can deform, and the air acts as a cushion aswell. If you imagine falling onto a brick wall that hurts way more than falling onto a soft matress. You have more time to slow down gently on the matress. So even though your whole momentum gets down to zero, it takes a longer time so the maximum force is smaller (but acts on you for longer)
Will try to answer as easy as possible.
To change the direction of an object depends on one thing: it’s weight (which it’s mass times acceleration), because depending the weight of it is directly proportional to the force required to change it’s direction and that object has resistance to that change. If the weight is little being directly proportional then the force on that object is small.
So even though your slap might have a big force, because the object(being) you are hitting is small only a small part of that force is transferred before it has the same direction as your slap and so the impact is smaller.
Will try to answer as easy as possible.
To change the direction of an object depends on one thing: it’s weight (which it’s mass times acceleration), because depending the weight of it is directly proportional to the force required to change it’s direction and that object has resistance to that change. If the weight is little being directly proportional then the force on that object is small.
So even though your slap might have a big force, because the object(being) you are hitting is small only a small part of that force is transferred before it has the same direction as your slap and so the impact is smaller.
The amount of force is distributed across the area of your hand. If the insect is small enough, there’s not a lot of force being applied to the area they occupy.
It’s the same idea that makes sharp objects able to cut things. You’re only applying a low amount of force but it’s focused into a tiny point, so it will rip through things very easily.
Bugs & insects also have an exoskeleton instead of a normal skeleton. So the force you apply is acting on the most rigid structure. If you hit a fleshy animal, you might not break a bone but you can cause other damage. If you hit a bug, you’ve gotta break that exoskeleton for it to really do anything. A small amount of force that is focused into its small area will probably do the job but if you’re wasting energy hitting a large surface area you will need a lot more force.
The amount of force is distributed across the area of your hand. If the insect is small enough, there’s not a lot of force being applied to the area they occupy.
It’s the same idea that makes sharp objects able to cut things. You’re only applying a low amount of force but it’s focused into a tiny point, so it will rip through things very easily.
Bugs & insects also have an exoskeleton instead of a normal skeleton. So the force you apply is acting on the most rigid structure. If you hit a fleshy animal, you might not break a bone but you can cause other damage. If you hit a bug, you’ve gotta break that exoskeleton for it to really do anything. A small amount of force that is focused into its small area will probably do the job but if you’re wasting energy hitting a large surface area you will need a lot more force.
For the same reason that a single Lego brick is indestructible no matter what bony part of your poor heel steps on it, but a full Lego structure will crumble into pieces and murder your whole family if left underfoot.
Force (f) = Mass (m) times Acceleration (a).
So the force something feels on impact is a product of how heavy it is and how fast it’s going when it hits.
Let’s pretend, just because it’s easier, that your hand is a stationary wall that the fly is flying into at the same speed as your previously swinging hand. So you take the speed of the object, and multiply it by its mass, which as I’m sure you’ve guessed is not a lot because it’s a fly. Since the fly’s mass is so teensy, it would take a *lot* more speed for it to feel much force at all from being swatted as you describe, because your hand doesn’t travel fast enough for that f=ma equation from earlier to yield a big enough number to do anything, but something like a car at highway speeds will.
For the same reason that a single Lego brick is indestructible no matter what bony part of your poor heel steps on it, but a full Lego structure will crumble into pieces and murder your whole family if left underfoot.
For the same reason that a single Lego brick is indestructible no matter what bony part of your poor heel steps on it, but a full Lego structure will crumble into pieces and murder your whole family if left underfoot.
One way to think of it is, people can get hit by waves on the beach. I’ve played a “game” in Hawaii where I’d let myself get by a wave, some were even taller than me. The water definitely weighed a lot more than me. But the effect was it would start pushing me up the beach.
It might seem a little weird to think of it this way, but humans are mostly made of water.
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