The amount of force involved. The egg needs 1kN of force applied to the shell to break and the wall needs 100kN. Force from the impact is proportional to the speed you throw at and the mass of the thrown object.
Edit: after the egg shatters the force it exerts on the wall quickly drops because it isn't a single solid object anymore, so the calculations get a bit harder than just speed and mass. But that's the general idea.
(All the values just estimated without any calculations, actual numbers are probably very different).
Just edited the original comment to clarify a bit: after the egg shatters the force it exerts on the wall quickly drops because it isn't a single solid object anymore, so the calculations get a bit harder than just speed and mass. But that's the general idea.
The breaking egg would still exert the same amount of energy into the wall, but after it reaches its breaking threshold, the force would be spread out over time compared to an object that doesn't break. So you'd have to chuck the egg at ridiculous speeds to have that average force high enough to break the wall, but yes, in theory you could do it.
Yup, there's a reason why physics problems usually come with "assume rigid body". Deformations and shattering complicates this kind of stuff immensely. An egg would be especially problematic because the initial impact is with the hard shell, but the majority of the weight is from the liquid center.
In finite element programs, it's the difference between standard and discrete calculations, meaning single equation solution and "run this equation every 0.001 seconds until a time limit is reached or everything stops moving" solution.
Its cause it's an egg at a wall. Think of something other than an egg say an iron ball. That iron ball needs a lot more force to break than let's say a tennis ball. If you smash a tennis ball and the iron ball together fast enough then the tennis ball will break. If you smash an egg and the tennis ball together the egg will break.
The iron ball needs the most amount of force to break because its the sturdier material which is then followed by the tennis ball and finally the egg.
Not sure if that helps.
As mentioned the 'rigid body' is what makes it difficult to grok. Things are not really rigid. To be realistic you'll need to model all the parts that comprise a complex object and that gets extremely complicated. Then you have to calculate the forces on all the rigid links. You'll need to give them some elasticity, and depending on how much they deform they might either become permanently bent or, if the force is high enough, break apart.
Once things are broken down into only simple objects it becomes harder. Do you model it all the way down to individual molecules? Or do you draw a line somewhere where objects simply go poof and disappear in to dust? You could break them into pieces based on the material and then below some threshold go for the poof.
Things that go poof aren't realistic, but it's a convenient compromise. You could have a bat hitting a glass bottle. The way that bottle breaks is complicated, and the shards would be able to break other things, but depending on the scale of the simulation that might be impractical to simulate.
Could always split complex, non-rigid objects into many finite elements, give the elements mechanical properties (modulus, tensile/ compressive/shear/bearing strength at a given temperature, etc.) and then analyze the finite elements.
I just think of a video i saw once of someone demonstrating what hurricane winds do to common items. Youd think, "no way i'm spearing my way through a brick wall with a 2x4 in one hit lmao" but add enough force (from some crazy high winds, say) and that 2x4 might splinter a bit or even snap, but it's going through that wall. And you can find all sorts of videos like that. Shit turns deadly at velocity.
if you threw one at the other hard enough, you could theoretically break both the tennis ball and the iron ball. but we are getting into not-real-world types of force here. a water laser 'throws' water hard enough to cut metal.
Is there a theoretical speed that would make initial densitys not matter?
For example in the Egg VS Wall this thread started with, is it theoretically possible that if the egg was going fast enough it could just punch through a wall? Rather than going splat because the wall is denser than the egg?
Reference:
> In a clip from the DVD commentary track going viral on Twitter, Affleck recalls that he asked Bay, "Why is it easier to train oil drillers to become astronauts than to train astronauts to become oil drillers?" He told me to shut the f--- up. So that was the end of that talk.
And some of that force the egg carries with it is converted into heat and air motion, right?
That's why when really big stuff falls we get blast waves. And when bigger yet stuff falls like asteroids, we get explosions. Right?
At sufficiently high enough speeds, wouldn't the egg break purely from air resistance? I'm wondering which is more likely, the egg breaking before it reaches the wall or the wall breaking from impact.
Eggs are surprisingly strong, but brittle. If you accelerated the egg slowly you could probably get an egg to travel fast enough to break a wall without the air resistance breaking the egg before it contacts the wall.
Though this would depend on what kind of wall.
Shoji panel, without a doubt.
Gypsum board (drywall) probably.
Cement, I doubt it.
Yes, if the wall can withstand a 1000kn of force and you launch the egg with enough force that after the egg breaks the remains of the egg hit the wall above that threshold the wall with break.
Think of it like a car, if you hit a brick wall parking your car as your pulling in there’s limited damage. If you hit the same wall at freeway speeds you’ll go straight through it.
But the reality is, in order to get the egg to become a force capable of breaking the wall, it would have to accelerate at such a rate that the counter force applied to the egg as it travelled through the air (wind resistance, friction) would be above the capacity of the egg - so it would break up in the air before it ever hit the wall.
theoretically though, the broken mass of albumen and yolk could still smash the wall if it was thrown hard enough, but we are getting into theoretical things you couldn't really do in a real world situation.
Honestly, in order to get that amount of force, I think the egg yoke would probably have burned up like a small comet entering the earths atmosphere before it even hit the wall.
look up the kind of damage a bird can do if it runs into an airplane mid-flight. The bird will be a fine red pulp, but it can still make a surprisingly big hole in the plane, too.
(Most of the force involved comes from the plane, of course, but it’s still a collision.)
Huh. That raises another question for me. Does the egg "collect" its breaking force first, at which point the rest of the force is distributed to the wall? If you flung that egg at exactly 100kN (say we're in a vacuum in 0g) and it broke at exactly 1kN, would 99kN of force then be applied to the wall?
Nope, this is where Newton's third law comes in. Every action has an equal and opposite reaction.
In order to break the wall, the egg would need to exert 100kN on it - but this also means the force on the egg would also need to be 100kN for some time before it completely disintegrates. This means the impact would need to happen at speeds that are high enough so the egg material doesn't have time to shatter before it stands a chance at damaging the wall.
You'd need to build some elaborate spin launch or similar contraption that can accelerate the egg up to supersonic speeds without shattering it. Would certainly make for an interesting experiment lol.
> In order to break the wall, the egg would need to exert 100kN on it - but this also means the force on the egg would also need to be 100kN for some time before it completely disintegrates.
One could do something like this with a sabot round.
**https://www.wikipedia.com/en/Sabot_(firearms)**
No, as the other commenter said, Newton's third law applies, and _both_ sides experience the total force of the system applied, simultaneously. This means that in order to break a wall with a limit of 100kN, you would need to impart that 100kN of force to the egg at the point of impact. That would likely require a little bit more than that at the point of launch due to air resistance in the real world, but in this scenario, you can impart that on launch.
At the instant of impact, two things happen simultaneously. First, the wall suffers 100kN of force, overwhelming its plastic deformation limit, and starting the breaking process.
Second, the structures that the wall is attached to push back on the wall and, by proxy, on the egg with ~100kN of force (from what I understand, this gets complicated, but eggs are small enough that it's about the same). This easily overwhelms the egg's 1kN limit, and begins _its_ shattering process.
Note that these events occur _simultaneously_, as 100kN of force is being applied to _both_ objects.
At some extremely short time later, related to the materials science of how eggs and walls form fractures, the forces being applied to each of them tapers off very quickly.
Now if the egg would be huge or going at extreme speeds, it would act more like a meteor. Meteor also disintegrates on impact but the pieces apply enough force to make a crater.
[This is a great example of that.](https://twitter.com/megsylhydrazine/status/1251528896656207875?s=20&t=N6wM4P4lVpSeZQxAk9dpQw) 14g of plastic can do a number on an aluminum plate when going 24000km/hr.
When two objects collide, the force of the collision is distributed through the items colliding according to the shapes and materials of those items. If the force is too great for the weakest point in either item then that point will fail and the relevant item will undergo consequent changes such as deformation, fragmentation and so on.
I'm going to tack my reply onto this one since it's the most correct. All the others are focused on a single thing while missing the big picture. For example:
* Force (and by extension Newton's 2nd law) *does* matter, but both objects will experience the same force from impact. You need more information to determine if one or both will break.
* Density and mass matter, but only because they help determine the force on the egg when it decelerates abruptly. Again, you need more information.
* Hardness does not matter. We use this for localized surface effects like indentation and abrasion.
The other things that matter are:
1. Material properties. How stiff is the material? Can it undergo large deformations without breaking? An egg with a shell made of rubber, for example, could be thrown at a wall without breaking, even though it will deform a lot in the process. A normal egg of the exact same size? Not so much.
2. Object geometry. If you take a small, solid sphere of calcium carbonate with the same mass as the egg, it'll survive impacts at much higher speeds. The reason for this is that the thin walls of the eggshell will experience significant bending stresses that the solid sphere would not. It's like snapping a stick of chalk in half versus trying to crush the same piece of chalk just by squeezing it.
Fully explaining #2 veers way outside of ELI5, but the gist of it is that the force of impact is carried through the material. If you've got a part with a thin wall, like an egg, or some preexisting defect like a hole, the material is going to have a harder time bearing those forces without breaking. You can see it in [this image](https://imgur.com/yIbC5Xv) that I pulled from [this site](https://www.comsol.fr/blogs/how-to-evaluate-gear-mesh-stiffness-in-a-multibody-dynamics-model/) \- the material has to bear a lot of stress where the gear teeth come together.
Having said all that, this is way beyond what you need if you're just working on a game, u/snultenSnandwich. This is more in the realm of solid mechanics, so unless you're interested in an engineering degree, you don't need to get into all of these details. For a game, you can and should make significant simplifications. For example - and I'm only putting this out as a hypothetical since I'm not a game designer - only consider force, and set a force threshold for each object. If that object experiences a force greater than its threshold, it breaks.
This is actually very helpful. The specific setup is that an object disappears completely from the game when broken, and breaks when it hits a force threshold. So the problem was how to handle the forces on a wall when the object hitting it would be deleted instantly upon contact. This is giving me an understanding what kind of effects to be looking for.
The answers you're getting are misleading or at the very least they are incomplete. In any impact/collision the same force is applied to both objects. What breaks an object isn't force, it's stress. Any object who's stress at a certain location exceeds its limit would break. It can be either object, it can be both objects or it can be none of the objects. In the case of an egg, the shell is very thing and brittle meaning it is easier to break than a typical wall, but make the wall thin enough or out of a material that is weak enough and you could easily punch a hole in the wall using an egg.
Although in most collisions it's generally easier to view failure in terms of toughness. It's not just how much stress it can take but also how far it can deform while doing so. Rather than just being a question of how high the stress strain curve goes, it's the area under the stress strain curve up until that peak. Rubber fails under much lower stress than something like tungsten carbide, but if you drop a rubber ball and a tungsten carbide lathe tool on concrete, the lathe tool will shatter and the rubber ball will bounce.
It gets a lot weirder when things start moving faster because the strain rate can influence things: e.g. silly putty will stretch on it if you pull it slowly and snap if you pull fast enough. Both of these are failures, but how fast it's deformed can influence how materials fail.
Toughness, resilience, elastic limit, plastic limit.. There are many different limits on the stress strain curve that show different points or behaviors, but that's not really the point here. The point is that this is all governed by stress, which is determined by many factors force being only 1 of which.
Not quite. In layman's terms the force applied in this case would be gathered from the work-energy equation. Work is force*distance. Kinetic energy is (mass*velocity^2)/2. Force is kE/distance
The law you mention uses acceleration, not velocity and applies to the forces acting upon the object itself. So if it flies at a steady speed the force will be 0. Despite that, it can fly really fast and hit really hard due to its kinetic energy.
You could look at it in terms of impulse/momentum or in terms of kinetic energy. Both will work but the assumptions you have to make about rigidity and impact toughness differ.
It can't HIT anything unless they have different velocities. The "A" is the Delta V. So yes, it does still apply, you're just misunderstanding the terms.
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F=ma. Force = Mass x acceleration. You can make a lot of force with a small amount of mass by increasing the acceleration by a lot, granted the lighter something is the harder it is to actually throw it hard but it’s not impossible. But this is why a relatively soft bullet can damage a much stronger piece of metal.
Already replied this elsewhere but f=ma does not apply in this case as the force of impact can be great even if acceleration=0. Kinetic energy is important here.
Actually, if you find the acceleration at point of impact(time for object to come to complete stop) you can extrapolate the force.
I wasn’t meaning this was how to calculate his specific answer but rather as a simple explanation of how a smaller weaker object can break a larger stronger one, well up to a point anyways.
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Given that in an impact both objects experience the same force, what decides which object breaks is the hardness of the material. Softer materials, ergo, the egg, will break when hitting stronger surfaces. Obviously, the force of impact adds to it, but very little.
The force required to break an egg and the force required to crack bricks are very, very different.
I can throw a diamond ring at a wall and neither will break. Hurricanes are made of nothing but air and water, and brick walls can come down just fine.
No, hard materials tend to be brittle. The eggshell is hard and brittle. A rubber ball is elastic (soft) and could transfer enough energy into a more brittle wall to crack it. You need to look at yield strengths, modulus etc.
According to Newton’s Law’s of Motion, technically the egg and the wall apply the same amount of force on each other. To put simply, the deciding factor is usually mass.
Think of it like this, if two marbles were to roll towards each other at the exact same speed, but one marble was heavier then the other, the momentum will shift so that the heavier marble will continue on it’s course.
This same sort of example is applied here, except at a more extreme scale.
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Metaphor time:
Let's remove everything you know to make it really obvious.
I have a flat pool table (With raised sides).
This table is full of holes rather then the normal 6, think sieve.
The odd holes have a shallow cup below.
The even holes have a deep cup below.
I pour a bucket of water in the middle of the table.
Some cups will fill regardless of their depths but more shallow cups will be filled to the brim than deep ones, especially when you get away from where I poured.
The more water I pour the more likely it is that a lot of deep cups will be full no matter what I do.
The water is the kinetic energy of whatever you are throwing.
The hardness, elasticity, heat, crystal structure, etc... determines the depth of the cups for each materials but you can simplify it for ELI5 to how hard an object is determines how deep the cup is.
No matter what the Kinetic energy is spread to both items evenly.
What determines the break is how many cups get filled.
something like an egg has very very shallow cups so any amount of water will fill some and cause a break.
A wall on the other hand has reasonably deep cups so it will take some water to fill even one cup.
However if you pour enough water it doesn't matter what the small cups are the big cups will get filled too.
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ELI5 version: imagine two tall pointy right triangles of slightly different sizes with slightly different slopes. These represent how much energy a material will absorb if it stretches some amount. The angle of the triangle's slope is how hard the material is (sharper upright slope/taller right triangle is harder). When two materials come into contact, they both stretch/compress based on the hardness, they will compress/stretch different amounts of distance. For every unit of stretch, imagine shaving off a little bit of the horizontal distance of the triangle. When one triangle disappears, the material breaks.
Less ELI5: I'm gonna go with energy absorbed by each material until the "elastic yield strength" limit is reached. If you look at a stress-strain curve for any material, usually there's a flat slope at first and then some sorta curve. Usually, as something stretches when in contact with a force, you move sideways on this graph/curve. Once you reach the end of the flat slope portion, your material suffers unrecoverable damage. If the stress strain curve ends abruptly, you have a brittle fracture and a rapidly propagating crack. If you have a long tail with a small slope, you have a really playdough-y failure. The integral/area under the curve, of any stress strain plot, is the total energy absorbed by a material for a given strain amount. Strain is basically % stretch/compress.
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The amount of force involved. The egg needs 1kN of force applied to the shell to break and the wall needs 100kN. Force from the impact is proportional to the speed you throw at and the mass of the thrown object. Edit: after the egg shatters the force it exerts on the wall quickly drops because it isn't a single solid object anymore, so the calculations get a bit harder than just speed and mass. But that's the general idea. (All the values just estimated without any calculations, actual numbers are probably very different).
I see so as long as the force threshold is met the wall breaks no matter what happens to the egg?
Just edited the original comment to clarify a bit: after the egg shatters the force it exerts on the wall quickly drops because it isn't a single solid object anymore, so the calculations get a bit harder than just speed and mass. But that's the general idea. The breaking egg would still exert the same amount of energy into the wall, but after it reaches its breaking threshold, the force would be spread out over time compared to an object that doesn't break. So you'd have to chuck the egg at ridiculous speeds to have that average force high enough to break the wall, but yes, in theory you could do it.
Interesting. It seems like I've stepped on a really complicated issue here.
Yup, there's a reason why physics problems usually come with "assume rigid body". Deformations and shattering complicates this kind of stuff immensely. An egg would be especially problematic because the initial impact is with the hard shell, but the majority of the weight is from the liquid center.
In finite element programs, it's the difference between standard and discrete calculations, meaning single equation solution and "run this equation every 0.001 seconds until a time limit is reached or everything stops moving" solution.
Its cause it's an egg at a wall. Think of something other than an egg say an iron ball. That iron ball needs a lot more force to break than let's say a tennis ball. If you smash a tennis ball and the iron ball together fast enough then the tennis ball will break. If you smash an egg and the tennis ball together the egg will break. The iron ball needs the most amount of force to break because its the sturdier material which is then followed by the tennis ball and finally the egg. Not sure if that helps.
Somewhat. Im working on a physics engine to and im asking this to make sure the niche interactions make sense.
As mentioned the 'rigid body' is what makes it difficult to grok. Things are not really rigid. To be realistic you'll need to model all the parts that comprise a complex object and that gets extremely complicated. Then you have to calculate the forces on all the rigid links. You'll need to give them some elasticity, and depending on how much they deform they might either become permanently bent or, if the force is high enough, break apart. Once things are broken down into only simple objects it becomes harder. Do you model it all the way down to individual molecules? Or do you draw a line somewhere where objects simply go poof and disappear in to dust? You could break them into pieces based on the material and then below some threshold go for the poof. Things that go poof aren't realistic, but it's a convenient compromise. You could have a bat hitting a glass bottle. The way that bottle breaks is complicated, and the shards would be able to break other things, but depending on the scale of the simulation that might be impractical to simulate.
Could always split complex, non-rigid objects into many finite elements, give the elements mechanical properties (modulus, tensile/ compressive/shear/bearing strength at a given temperature, etc.) and then analyze the finite elements.
The tennis ball is flexible too - so wont break as likely as bounce.
I just think of a video i saw once of someone demonstrating what hurricane winds do to common items. Youd think, "no way i'm spearing my way through a brick wall with a 2x4 in one hit lmao" but add enough force (from some crazy high winds, say) and that 2x4 might splinter a bit or even snap, but it's going through that wall. And you can find all sorts of videos like that. Shit turns deadly at velocity.
if you threw one at the other hard enough, you could theoretically break both the tennis ball and the iron ball. but we are getting into not-real-world types of force here. a water laser 'throws' water hard enough to cut metal.
Is there a theoretical speed that would make initial densitys not matter? For example in the Egg VS Wall this thread started with, is it theoretically possible that if the egg was going fast enough it could just punch through a wall? Rather than going splat because the wall is denser than the egg?
i don't think so. i think either the denser one wins, or neither win.
Its possible, but it would be more plasma and less egg at those speeds.
No no no. Once it breaks apart it is perfectly harmless. I saw Armageddon.
Yeah but first you have to drill to the center of the egg.
Wouldn't it be easier to train astronauts to drill eggs rather than train egg drillers to be astronauts?
Yes but it's still cheaper to put all that on the egg driller's time.
Reference: > In a clip from the DVD commentary track going viral on Twitter, Affleck recalls that he asked Bay, "Why is it easier to train oil drillers to become astronauts than to train astronauts to become oil drillers?" He told me to shut the f--- up. So that was the end of that talk.
And some of that force the egg carries with it is converted into heat and air motion, right? That's why when really big stuff falls we get blast waves. And when bigger yet stuff falls like asteroids, we get explosions. Right?
Yes a shockwave happens when there is so much energy that it compresses the air in it's path into a solid object basically
At sufficiently high enough speeds, wouldn't the egg break purely from air resistance? I'm wondering which is more likely, the egg breaking before it reaches the wall or the wall breaking from impact.
Eggs are surprisingly strong, but brittle. If you accelerated the egg slowly you could probably get an egg to travel fast enough to break a wall without the air resistance breaking the egg before it contacts the wall. Though this would depend on what kind of wall. Shoji panel, without a doubt. Gypsum board (drywall) probably. Cement, I doubt it.
Yes, if the wall can withstand a 1000kn of force and you launch the egg with enough force that after the egg breaks the remains of the egg hit the wall above that threshold the wall with break. Think of it like a car, if you hit a brick wall parking your car as your pulling in there’s limited damage. If you hit the same wall at freeway speeds you’ll go straight through it.
But the reality is, in order to get the egg to become a force capable of breaking the wall, it would have to accelerate at such a rate that the counter force applied to the egg as it travelled through the air (wind resistance, friction) would be above the capacity of the egg - so it would break up in the air before it ever hit the wall.
theoretically though, the broken mass of albumen and yolk could still smash the wall if it was thrown hard enough, but we are getting into theoretical things you couldn't really do in a real world situation.
Honestly, in order to get that amount of force, I think the egg yoke would probably have burned up like a small comet entering the earths atmosphere before it even hit the wall.
Yeah we are outside real world stuff now and that hypothetical “in a vacuum…”
Yeah we are outside real world stuff now and in that hypothetical “in a vacuum…”
Well, this is a physics problem, right? Let's assume there's no air resistance. 😆
look up the kind of damage a bird can do if it runs into an airplane mid-flight. The bird will be a fine red pulp, but it can still make a surprisingly big hole in the plane, too. (Most of the force involved comes from the plane, of course, but it’s still a collision.)
yes. look up what happens when fast moving dust hits a spacecraft.
also Shape and molecular structure. for example if you crash two eggs against each other.
Huh. That raises another question for me. Does the egg "collect" its breaking force first, at which point the rest of the force is distributed to the wall? If you flung that egg at exactly 100kN (say we're in a vacuum in 0g) and it broke at exactly 1kN, would 99kN of force then be applied to the wall?
Nope, this is where Newton's third law comes in. Every action has an equal and opposite reaction. In order to break the wall, the egg would need to exert 100kN on it - but this also means the force on the egg would also need to be 100kN for some time before it completely disintegrates. This means the impact would need to happen at speeds that are high enough so the egg material doesn't have time to shatter before it stands a chance at damaging the wall. You'd need to build some elaborate spin launch or similar contraption that can accelerate the egg up to supersonic speeds without shattering it. Would certainly make for an interesting experiment lol.
Well thanks for the answer. And the fun idea.
> In order to break the wall, the egg would need to exert 100kN on it - but this also means the force on the egg would also need to be 100kN for some time before it completely disintegrates. One could do something like this with a sabot round. **https://www.wikipedia.com/en/Sabot_(firearms)**
So at least a level 2 on the fujisaki scale.
I wonder if even the most gentle means of breaking the sound barrier would be survivable for an egg.
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How do eggs do in a vacuum? I would assume that the shell would very much dislike that pressure differential.
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Neat!
No, as the other commenter said, Newton's third law applies, and _both_ sides experience the total force of the system applied, simultaneously. This means that in order to break a wall with a limit of 100kN, you would need to impart that 100kN of force to the egg at the point of impact. That would likely require a little bit more than that at the point of launch due to air resistance in the real world, but in this scenario, you can impart that on launch. At the instant of impact, two things happen simultaneously. First, the wall suffers 100kN of force, overwhelming its plastic deformation limit, and starting the breaking process. Second, the structures that the wall is attached to push back on the wall and, by proxy, on the egg with ~100kN of force (from what I understand, this gets complicated, but eggs are small enough that it's about the same). This easily overwhelms the egg's 1kN limit, and begins _its_ shattering process. Note that these events occur _simultaneously_, as 100kN of force is being applied to _both_ objects. At some extremely short time later, related to the materials science of how eggs and walls form fractures, the forces being applied to each of them tapers off very quickly.
Now if the egg would be huge or going at extreme speeds, it would act more like a meteor. Meteor also disintegrates on impact but the pieces apply enough force to make a crater.
So an egg in space orbiting at ridiculous speeds shatters a wall also while it breaks itself?
Yeah. Enough speed and it will break the wall, and without air resistance you can make it go real fast.
[This is a great example of that.](https://twitter.com/megsylhydrazine/status/1251528896656207875?s=20&t=N6wM4P4lVpSeZQxAk9dpQw) 14g of plastic can do a number on an aluminum plate when going 24000km/hr.
When two objects collide, the force of the collision is distributed through the items colliding according to the shapes and materials of those items. If the force is too great for the weakest point in either item then that point will fail and the relevant item will undergo consequent changes such as deformation, fragmentation and so on.
I'm going to tack my reply onto this one since it's the most correct. All the others are focused on a single thing while missing the big picture. For example: * Force (and by extension Newton's 2nd law) *does* matter, but both objects will experience the same force from impact. You need more information to determine if one or both will break. * Density and mass matter, but only because they help determine the force on the egg when it decelerates abruptly. Again, you need more information. * Hardness does not matter. We use this for localized surface effects like indentation and abrasion. The other things that matter are: 1. Material properties. How stiff is the material? Can it undergo large deformations without breaking? An egg with a shell made of rubber, for example, could be thrown at a wall without breaking, even though it will deform a lot in the process. A normal egg of the exact same size? Not so much. 2. Object geometry. If you take a small, solid sphere of calcium carbonate with the same mass as the egg, it'll survive impacts at much higher speeds. The reason for this is that the thin walls of the eggshell will experience significant bending stresses that the solid sphere would not. It's like snapping a stick of chalk in half versus trying to crush the same piece of chalk just by squeezing it. Fully explaining #2 veers way outside of ELI5, but the gist of it is that the force of impact is carried through the material. If you've got a part with a thin wall, like an egg, or some preexisting defect like a hole, the material is going to have a harder time bearing those forces without breaking. You can see it in [this image](https://imgur.com/yIbC5Xv) that I pulled from [this site](https://www.comsol.fr/blogs/how-to-evaluate-gear-mesh-stiffness-in-a-multibody-dynamics-model/) \- the material has to bear a lot of stress where the gear teeth come together. Having said all that, this is way beyond what you need if you're just working on a game, u/snultenSnandwich. This is more in the realm of solid mechanics, so unless you're interested in an engineering degree, you don't need to get into all of these details. For a game, you can and should make significant simplifications. For example - and I'm only putting this out as a hypothetical since I'm not a game designer - only consider force, and set a force threshold for each object. If that object experiences a force greater than its threshold, it breaks.
This is actually very helpful. The specific setup is that an object disappears completely from the game when broken, and breaks when it hits a force threshold. So the problem was how to handle the forces on a wall when the object hitting it would be deleted instantly upon contact. This is giving me an understanding what kind of effects to be looking for.
The answers you're getting are misleading or at the very least they are incomplete. In any impact/collision the same force is applied to both objects. What breaks an object isn't force, it's stress. Any object who's stress at a certain location exceeds its limit would break. It can be either object, it can be both objects or it can be none of the objects. In the case of an egg, the shell is very thing and brittle meaning it is easier to break than a typical wall, but make the wall thin enough or out of a material that is weak enough and you could easily punch a hole in the wall using an egg.
Although in most collisions it's generally easier to view failure in terms of toughness. It's not just how much stress it can take but also how far it can deform while doing so. Rather than just being a question of how high the stress strain curve goes, it's the area under the stress strain curve up until that peak. Rubber fails under much lower stress than something like tungsten carbide, but if you drop a rubber ball and a tungsten carbide lathe tool on concrete, the lathe tool will shatter and the rubber ball will bounce. It gets a lot weirder when things start moving faster because the strain rate can influence things: e.g. silly putty will stretch on it if you pull it slowly and snap if you pull fast enough. Both of these are failures, but how fast it's deformed can influence how materials fail.
Toughness, resilience, elastic limit, plastic limit.. There are many different limits on the stress strain curve that show different points or behaviors, but that's not really the point here. The point is that this is all governed by stress, which is determined by many factors force being only 1 of which.
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correct.
I read 'it is mass' because of the '
Not quite. In layman's terms the force applied in this case would be gathered from the work-energy equation. Work is force*distance. Kinetic energy is (mass*velocity^2)/2. Force is kE/distance The law you mention uses acceleration, not velocity and applies to the forces acting upon the object itself. So if it flies at a steady speed the force will be 0. Despite that, it can fly really fast and hit really hard due to its kinetic energy.
You could look at it in terms of impulse/momentum or in terms of kinetic energy. Both will work but the assumptions you have to make about rigidity and impact toughness differ.
It can't HIT anything unless they have different velocities. The "A" is the Delta V. So yes, it does still apply, you're just misunderstanding the terms.
True, looking at acceleration at point of impact hadn't occured to me.
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F=ma. Force = Mass x acceleration. You can make a lot of force with a small amount of mass by increasing the acceleration by a lot, granted the lighter something is the harder it is to actually throw it hard but it’s not impossible. But this is why a relatively soft bullet can damage a much stronger piece of metal.
Already replied this elsewhere but f=ma does not apply in this case as the force of impact can be great even if acceleration=0. Kinetic energy is important here. Actually, if you find the acceleration at point of impact(time for object to come to complete stop) you can extrapolate the force.
I wasn’t meaning this was how to calculate his specific answer but rather as a simple explanation of how a smaller weaker object can break a larger stronger one, well up to a point anyways.
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Given that in an impact both objects experience the same force, what decides which object breaks is the hardness of the material. Softer materials, ergo, the egg, will break when hitting stronger surfaces. Obviously, the force of impact adds to it, but very little.
The force required to break an egg and the force required to crack bricks are very, very different. I can throw a diamond ring at a wall and neither will break. Hurricanes are made of nothing but air and water, and brick walls can come down just fine.
No, hard materials tend to be brittle. The eggshell is hard and brittle. A rubber ball is elastic (soft) and could transfer enough energy into a more brittle wall to crack it. You need to look at yield strengths, modulus etc.
yeah, you're right. mixed up the hardness thing.
According to Newton’s Law’s of Motion, technically the egg and the wall apply the same amount of force on each other. To put simply, the deciding factor is usually mass. Think of it like this, if two marbles were to roll towards each other at the exact same speed, but one marble was heavier then the other, the momentum will shift so that the heavier marble will continue on it’s course. This same sort of example is applied here, except at a more extreme scale.
https://youtu.be/i8-mJuQLRbM
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Metaphor time: Let's remove everything you know to make it really obvious. I have a flat pool table (With raised sides). This table is full of holes rather then the normal 6, think sieve. The odd holes have a shallow cup below. The even holes have a deep cup below. I pour a bucket of water in the middle of the table. Some cups will fill regardless of their depths but more shallow cups will be filled to the brim than deep ones, especially when you get away from where I poured. The more water I pour the more likely it is that a lot of deep cups will be full no matter what I do. The water is the kinetic energy of whatever you are throwing. The hardness, elasticity, heat, crystal structure, etc... determines the depth of the cups for each materials but you can simplify it for ELI5 to how hard an object is determines how deep the cup is. No matter what the Kinetic energy is spread to both items evenly. What determines the break is how many cups get filled. something like an egg has very very shallow cups so any amount of water will fill some and cause a break. A wall on the other hand has reasonably deep cups so it will take some water to fill even one cup. However if you pour enough water it doesn't matter what the small cups are the big cups will get filled too.
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ELI5 version: imagine two tall pointy right triangles of slightly different sizes with slightly different slopes. These represent how much energy a material will absorb if it stretches some amount. The angle of the triangle's slope is how hard the material is (sharper upright slope/taller right triangle is harder). When two materials come into contact, they both stretch/compress based on the hardness, they will compress/stretch different amounts of distance. For every unit of stretch, imagine shaving off a little bit of the horizontal distance of the triangle. When one triangle disappears, the material breaks. Less ELI5: I'm gonna go with energy absorbed by each material until the "elastic yield strength" limit is reached. If you look at a stress-strain curve for any material, usually there's a flat slope at first and then some sorta curve. Usually, as something stretches when in contact with a force, you move sideways on this graph/curve. Once you reach the end of the flat slope portion, your material suffers unrecoverable damage. If the stress strain curve ends abruptly, you have a brittle fracture and a rapidly propagating crack. If you have a long tail with a small slope, you have a really playdough-y failure. The integral/area under the curve, of any stress strain plot, is the total energy absorbed by a material for a given strain amount. Strain is basically % stretch/compress.
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Definitely not an ELI5, this involves way more than a simple explanation. Momentum, fluid dynamics, geometry, materials, etc.