5 votes

Any Math & Physics Experts Around Here?

This pressure cooker lid at the Boston Bombing has me thinking.

What would the force have to be from a bomb so that the pressure cooker lid would end up 35 yards away and 6 stories up, landing on the roof of a building?

I don't know the math formula to figure this one out.

We have a pressure cooker, with the lid presumably locked to the main part of the device, inside a zipped backpack, and a bomb inside. The thing explodes, separating the lid from the main part of the device, and the lid ends up about 100 feet away and around 50-60 feet up (probably had to go 50-100 feet in the air) to land on a 6-story building's roof.

What would the force have to be? And then with that force, what sort of collateral damage SHOULD we see in the immediate area where the main part of the pressure cooker and whatever was inside of it went?

Can anybody around here do the math on that?

Here is information about where the lid was found:

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Doesn't sound like much force ...

... would it matter that the lid was likely locked to the main part of the pressure cooker?

A pressure cooker lid is locked on tight.

So a lot of force would be needed to begin with. People who have the lids blow off in the kitchen get quite a damaged ceiling and this is just steam. I read that the CIA trained Afghanistan operatives to make theses pressure cooker bombs.

If the lid was locked on

If the lid was locked on tightly, that would matter a great deal because it means more initial force was needed to break the seal.

To climb the mountain, you must believe you can.

I'll try

I'll crunch some numbers and see what I can come up with.

Plots of the trajectory will cost you extra.

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I Passed physics with a 80...

but here's some advice to get going.

Since the cooker is not moving, it has zero force.. F(force) = M(mass) * A(Acceleration).. F = MA ... Since the mass of a cooker is N lbs and the acceleration is 0 (not moving), the force is zero.

In order to move the cooker 6 floors, 6*12 = 72' + parapet 3' = 75' in total, the force of the blast would have to be pretty intense, as seen.

This where I get a B and others get an A.

They that give up liberty for security deserve neither.

Just enough to blow someone's

Just enough to blow someone's legs off and kill a few people.

not an expert

but a 6 story building is not 500 feet tall. an average story is 10-12 feet.

so 60-70 feet.

the average man could throw a lid about 40-50, so not much force at all.

Good catch ...

... I had an extra zero there. I am assuming 8-10 feet per story.


Think of ceiling heights...

though you may live in a hobbit house.. and that's cool.

They that give up liberty for security deserve neither.

i've heard

also that they were placed at a diagonal angle, as to direct the shrapenel up toward the audience. so a diagonal trajectory of 35 yards (roughly 110 feet) and a vertical climb of roughly 70 feet, this probaly would not take much force at all.

How about the opinion of a pressure-cooking phobic housewife?

Those things are CRAZY. The only reason I am willing to learn to use one is I can set up an outdoor kitchen, I would not run one in my house.
Now, younger women may laugh at me, the newer ones are supposedly much safer, but I am old enough to remember when housewives blew their kitchens to smithereens with them.
I also used to work with autoclaves, and anyone who works with them very long has a healthy respect for them, too. 3 days ago, I would have told you they could not become pressurized without a stove... Thanks to the media spelling out a nice little recipe, now I understand, and I do think you could get some pressure built up with household items. Unlike the media. I will decline to spell it out.
Keep digging for someone who can do the math, but I would not be surprised if that kind of pressure was possible.

Love or fear? Chose again with every breath.

I never knew anyone that blew up their kitchen,

but I was at Grandma's in the 1970s when she was canning and the safety plug blew out and put a hole in the ceiling. The safety plug back then were little round chunks of metal and made quite the ballistic projectile.

The newer canners I've seen have round rubber plugs that begin to seal as the pressure increase, and presumably would cause less damage if they blew out. Some even have an interlock that prevents removing the lid while it's still pressurized.

My wife does the canning, and would recommend choosing a canner with the "jiggle" weight instead of a pressure gauge. That way you can hear when the pressure comes up to start timing your batch. And if the noise stops - you have a problem (burner blew out, orifice clogged, etc.). And the jiggle weights don't need to be regularly re-calibrated like the dials. I know - more than you wanted to know about canning.

Actually, much appreciate.

I do water bath canning, and have promised myself to do pressure canning this year. We lost a freezer full of chickens we raised last year, I am canning some of them this time.

Love or fear? Chose again with every breath.

mountaincat's picture

The one I use

is older than me, over half a century.

Pressure cookers are great more making home distilleries...

for.... um.... distilling water! Yeah, that's it water, it's alright ATF, it's just very harsh tasting water, not untaxed liquor or anything.

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Were you on that TV show "Moonshiners?"