# Explosion force is dependent on the Amount and the said Material

1. Jan 11, 2014

### DaneS

As I understand it; when an explosive material is set off, the force is dependent on the Amount and the said Material.

As an example,
I have 2cm3 of dynamite

I set it off and once the appropriate "oo's and ahh's" are said I set up eight separate 1cm3 blocks of dynamite and set them up stacked as close as possible together and to explode at the same time.

Would the force be the same as the before mentioned 2cm3 block or would it be just eight separate outputs of force of the eight individual 1cm3 blocks set off together?

Obviously if I set off the eight 1cm3 blocks individually it would just be the force of 1block, eight times, but does sticking them together ie, 2 blocks (2x1cm3) create the singular output force of 2 or just two separate singular force outputs of 1?

Okay, if I confused you then hopefully you can understand my confusion.. (?)

I'll try break it down:

Explosion1 = One 2cm3 block
The singular force of Explosion1 has an output of 8

Explosion2 = Eight 1cm3 blocks together
Question 1 Does it equal a singular force of 8 or does it equal eight separate outputs of 2 alongside each other?

Explosion3 = One 2cm3 block AND One 1cm3 block on top
Question 2 Does it equal a singular output force of 9 OR two separate outputs of 8 and 1 respectively?

I hope SOMEONE who understands this can help me, I've been stuck on this during the holidays and my limited yr10 level physics doesn't help me, hopefully in this new year I might understand more.

Last edited: Jan 12, 2014
2. Jan 11, 2014

### HallsofIvy

Not "cm2"- you mean "cm3".

What "force" are you talking about. And what would distinguish four separate "lots" of "force" form one?

Again, what force and how is "double the output force" different from "two lots of it"?

3. Jan 11, 2014

### elegysix

Think of it like putting rocks on a waterbed. if the rocks are spread out, there will be many small weights over a large area, and the top of the waterbed will still be relatively flat. However, if there are many rocks in a small area, they will weigh down and cause the water bed to be shaped like a funnel.

The depth of the surface of the waterbed is analogous to your force. i.e. the higher the density of explosives in a region, the more force immediately surrounding it when exploded.

I would imagine the force due to an explosive (at some fixed distance/geometry) varies with the density of explosives exponentially... so summing the forces due to small amounts of explosives probably won't equal that due to a larger amount. But I'm just speculating.

Last edited: Jan 12, 2014
4. Jan 12, 2014

### DaneS

Corrected original post, I got lost when I posted it.

Last edited: Jan 12, 2014
5. Jan 12, 2014

### DaneS

I mean the pressure created by the explosion, and when I say the "singular output force" I mean is it all added up? or is it just two separate pressure waves?

It would be nice if you wouldn't try pick apart every little mistake in my question, cause if I knew what I was talking about, then I wouldn't be asking it in the first place!

6. Jan 12, 2014

### nbo10

What is sounds like your asking is: Can you reach the same physical state through multiple lower amplitude shocks as would be reached through a single higher amplitude shock?

7. Jan 13, 2014

### DaneS

Well, I guess so, that's why I'm asking cause I have no idea! Thank you for replying and somehow simplifying my complicated question!

8. Jan 13, 2014

### cjl

When you say "2cm3", do you mean 2 cubic centimeters, or a cube that is 2 centimeters on a side? Because that changes the answer...

If you mean the latter, then it would produce a shock very similar to the shock produced by 8 separate 1cm3 blocks placed close together. If you mean the former, the 8 smaller blocks would produce a significantly stronger shock, on account of the fact that there is significantly more explosive present.

9. Jan 15, 2014

### elegysix

Sounds to me like the question is -

Assuming a fixed total volume of explosives,
Is the sum of "forces" due to fractions of the volume (ignited seperately) equal to the "force" observed when igniting the whole volume at once.

where "force" is somewhat ambiguous.

If we're talking about pressure waves, let's say explosion 1 (E1) creates a maximum pressure P1, and explosion 2 (E2) creates a maximum pressure P2.

supposing a 3rd explosion (E3), which has the sum of the volumes of explosives in E1 and E2,

I would not assume that P3=P1+P2

Superposition does not hold for extreme pressures / shock waves.