# Quantifying explosions - how to determine force/pressure/etc?

1. Jun 16, 2009

### denver75

We're doing another demonstration about explosives, discussing the forces created.

Our primary explosive is PETN (detcord) - handled by a licensed technician of course.

I need to prepare some facts about the physical forces at play with the explosions. How can I quantify the energy expended? I've been digging around and the only statistic that is readily available is the rate of detonation. However, as more explosive material is used, the rate of detonation doesn't increase, but the explosion does.

Any info/facts/stats/formulas that might get me on the right path?
Thanks!
-D75

2. Jun 16, 2009

### Civilized

I don't have any expertise in this area, but I do recall that the equation:

$$R = (\frac{E t^2}{\rho}})^{\frac{1}{5}}$$

where R is the radius of the explosion at time t, E is the released in the explosion, and $\rho$ is the ambient density of air in the vicinity, was correctly used by a physicist who wasn't working on the Manhattan project to determine the energy released in the trinity test based on measurements of R vs t, although the value for the total energy was classified for decades, this method yields the answer within 10%. By the way, the formula should also apply for light explosives too.

I will wait for others to say more, since I don't know much about explosives.