North Tower Acceleration

[William Seger]

184. No!

As OTOH notes, you are misunderstanding Greening. There is no "distinction between fracturing and pulverization" which is exactly WHY Greening can use fracturing energy per unit area to calculate pulverization energies, by simply multiplying that fracturing energy by the surface area of the pulverized particles.

> Greening as well makes a further distinction for elastic strain of the concrete. So this presumably is also not factoring into the momentum loss estimates. Nor are the elastic and plastic strains for the columns. So these are all factored outside of the original momentum loss, yet you don't seem to have a problem with any of the others. Why are you picking on the concrete pulverization?

(Sigh.) I'm "picking on the concrete pulverization" because Ross included it in his "energy summary" even though he had already taken "momentum losses." As I have repeatedly (but futilely) pointed out to you, the kinetic energy in Ross' "momentum losses" number is ALL of the kinetic energy present before the collision but gone SOMEWHERE else after the collision. There IS no other source of energy to pulverize the concrete. A relative small amount of energy was converted to sound, vibration, and heat energy, but most of it was used in "deforming" stuff. Greening is attempting to directly calculate how much kinetic energy was dissipated by fracturing concrete, so he isn't concerned with momentum losses at all. I don't know what "distinction" you think you see, but he talks about the strain energy in the concrete only because that's where the fracturing energy really comes from: Some of the kinetic energy from the collision is converted into strain energy in the concrete and at some level of strain energy, you get fracturing.

> As it is explained to me, the momentum loss that Ross calculates is simply the energy expended bringing the lower mass up to the speed of the impacting mass.

No, the impacted mass gets velocity from direct momentum transfer. In an elastic collision, there is no kinetic energy lost and yet the impacted mass gets velocity. How could that possibly happen according to your understanding?

(Edit: OTOH types faster )