Smashing windows with spark plug powder

[Sanjøy]

Lad in the office claims that ground up ceramic material from spark plugs can be thrown at windows and they smash.

Fact or fiction

[Titanium S1 111S (gla)]

If it is thrown hard enough I would have thought it might be true but it would have to be 1000's of m/s.

We would be talking about an energy relationship with velocity and mass. If a stone is ten grams and is thrown at 2 meters per second and breaks a window then you would have to have a very fast piece of spark plug dust hitting the window to have the same energy. Even if you work on the principal that the force is being applied over a much smaller surface area and is therefore more effective in window breaking terms you would need to throw at enormous velocity.

I can’t think of any electrical or chemical characteristic of ceramic spark plus material which would take us away from conventional analysis.(interested to hear if anyone else can)

I recon he is taking sh1t.

[MacK]

Fact;

Taking the ceramic off the spark plug will leave the metal bits of the spark plug, which if thrown at a 'normal' window with any reasonable amount of force, should break it.

[robin]

That will be why whenever they want to make better bullets/shells they make them smaller - not

Smaller objects carry less kinetic energy than larger ones. If you cut a large object into quarters and throw them all at once, they will start (in total) with the same kinetic energy as they would have when they were still one object, but the increased surface area introduced by all the cuts will cause more drag so they will slow down more quickly (assuming we're talking in air here).

Thus they will arrive at the target slower, and all other things being equal, they will cause less damage. The more you cut them up, the more pronounced this effect will be.

In a vacuum you can make a hole in glass with a tiny piece of grit, provided you have a way of accelerating the grit to a high enough speed. In air, I think it would be practically impossible at any distance other than point blank, and even then you would need to use compressed air to accelerate and carry the particles at the required speed (like a sand blasting machine).

In short, if you have a spark plug and a window to break, throw one against the other

Cheers,
Robin

[tenkfeet]

Use an automatic centre punch , much more effective.

[Rich H]

Ground up it would be useless but broken into chunks works, have seen a demo on TV.

the problem is not the relative mass of the item, as clearly the mass of a tiny piece of ceramic won't smash a window, the issue is pressure.

The tiny mass thrown at the window is (hopefully if your a tea leaf!) concentrated on a tiny point as the ceramic spark plug will break into irregular pieces. the construction of a side window is such that even a small break will shatter the whole window (So you don't get skewered by large bits) if you can generate a high enough pressure anywhere on the glass it will break and take the whole window out.

this is why a brick may bounce off (high mass but lower pressure as the initial impact will "blunt" the brick as it is softer than the glass, spreading the load over a larger area and lowering the pressure) but a tiny piece of ceramic will break it (the ceramic is harder than the glass so will not "blunt" as easily). Take a hammer to a side window (someone else's ) and it takes quite a blow if the face is flat to the window, now take a emergency hammer which weights FA and try it (the other side perhaps?)


HTH
Rich
/pikey car tea leaf (Part time)

[Caveat Lector]

the problem is not the relative mass of the item, as clearly the mass of a tiny piece of ceramic won't smash a window, the issue is pressure.

The relative mass is a factor here as pressure = Force/Area and Force = Mass x Acceleration (or in this case deceleration as the object slows down from whatever speed it was doing to effectively zero). So in order to have a high pressure you need either a high mass or a small area, or even better both.

[Rich H]

The idea being that the chips of ceramic have v.sharp and v.hard edges creating v.small area and so a v.high pressure on impact

v.

[jj]

There is a video of everything on youtube......

http://www.youtube.com/watch?v=khayfayzXK8

[Kev]

Use an automatic centre punch , much more effective.

That'll be why they all disappeared from the workshop at the college I went to during my apprenticeship. Quite funny how they all disappeared in the first week of term.

I know the spark plug is the tool of the trade, for smash and grabs at traffic lights and stop junctions in South Africa. Seen it happen last time I was in Cape Town, car in front stopped at a red light, local walked up to the pax window, smash, then ran off with a handbag. It happened so quick. Fooking scary seeing it happen though. Then I realised why my mates tool of the trade is this



He works as an armed response security guard and is a major gun fanatic!!!