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5

No, it's not possible. The general rule of strength in foams is $\rho^3\propto\sigma^2$ so if you cut the density by a factor of 4, then your strength would be cut by a factor of 8. From a conceptual standpoint slicing a organized shape under a tensile load by a plane perpendicular to the load will show that there are $n$ discrete elements, all under a ...


3

I did some research and it seems that superhydrophobic coating can be used to decrease drag forces to a certain extent because the coating repels the water. It creates an air layer between the surface and the water that causes slip through two-phase flow. This allows the ship to slip past the water.


2

Long ago I worked at a military base and we had a room size vault. We had quantitative estimates of how long it would take to penetrate the vault under various senarios (techniques that focused on the lock or other parts). The estimates were in the 10-20 hour range, I don't remember exactly. In any case, it is possible to drill through the various forms ...


2

In short, to my understanding: homogeneous : the property is not a function of position, i.e. it does not depend on $x$, $y$ or $z$. isotropic: the property does not depend on a particular direction. NB: you can have a homogenous property that is not isotropic, i.e. the refractive index of a birefringent material: it is a constant, but this constant has ...


1

My guess is that the foam has some type of sillica in it which may stick to the knife having a detremental effect on its cutting ability possibly cleaning the blades regularly with alcohol could help this but i'm no chemist, hopefully this is helpful


1

I believe that one could rephrase the question as "if the limit of the speed of sound in a medium must be the speed of light in vacuum, what does that mean for the limit on rigidity of an object?" Speed of sound is given by $$c=\sqrt{\frac{E}{\rho}}$$ - it depends on both density and Young's modulus. I would consider "rigidity" to be just the modulus, and ...



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