Like when something gets shot is it the kinetic energy of the bullet or it’s momentum or the force or something else? What determines how much damage does the bullet do?
In: Physics
Like everything in life, GURPS has a spreadsheet for that: https://gamingballistic.com/2013/08/01/ballistics-spreadsheet-july-2013/
The most important elements are the velocity of the projectile, and it’s composition – in the case of a solid or jacketed projectile mass is the biggest factor, although hollow point projectiles will obviously do more damage through fragmentation – even with lower mass – assuming an unarmoured target
“Damage” needs to be strictly defined in order to conclusively answer this. If we don’t do this, we can end up with a pretty minor amount of damage tearing the jugular artery, but hey, it’s lethal anyway.
Eventually. With a physical material, you will have the nature of force you exert on it, and the material’s resistance to various types of forces. There’s shear force, tension, compression, friction, etc. A material that chips easily can be very resistant to tension or compression stress, while easily bendable material can be very susceptible to cutting force. Once you’ve decided with the type of force you’re applying and the material you’re destroying, you’ll be able to establish how much you will need to exert to produce the desired damage.
That sort of depends on what you understand as “damage”. Is a clean hole a lot of damage or very little damage in your opinion?
So for the sake of discussion, I’ll assume you mean “how badly the target is mangled”, and a clean hole counts as “little damage”. That’s how most people interpret that.
In that case, how much of the kinetic energy can be transferred from the projectile into damaging the target.
So a projectile that makes a tiny hole carries on with most of its kinetic energy intact.
But a projectile that doesn’t manage to punch through cleanly instead is forced to dump most of its energy into the target, damaging it.
How and why either result happens is unfortunately a very complex topic that I’m personally not sure how to ELI5, because even the same projectile will penetrate differently based on speed alone, but the shapes and materials make a massive difference too.
A most determinant factor is the ability of either material to deform and absorb the shock.
Throw a metal ball in a clothe sheet, the sheet will bend and not rupture.
Throw the same ball to a window, and the window will likely break, because the glass isn’t able to bend as much. And neither is the metal.
Throw a soft ball to the window, and the ball will likely squish, then bounce.
There’s no short answer to this. To analyze ‘damage’ we normally turn to simulations or practical testing.
Simulations usually involve creating a program that accurately simulates every element (for instance every beam and panel in the front of a car). Then simulating the movement and deformation of each piece using the very simple equations of force most people learn in school.
Often, from simulations and real testing, we can draw up heuristics – approximations using math that are based on the test results. In some circumstances, we can draw conclusions like “faster cars take more damage” or “more rigid cars injure passengers more” or even “larger bullets injure people more”. Sometimes we can even get equations, like “the depth a projectile penetrates into a material scales linearly with its density and length” but even these are limited to specific situations.
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