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And, if so, how much lift does it produce per cubic meter? (let's say at 290ish K and 150 meters above sea level)

For context, I'm taking an intro-level physics class. While I know what a joule is, I feel like I haven't really been able to internalize its meaning. Same goes for a couple of other SI units. This will probably improve with time, but that takes too long. And, as helpful as the Wikipedia "orders of magnitude" series has been, sometimes the mind's eye just doesn't cut it.

So, I'm making a real-life version of it (that may or may not become a YouTube video, depending on my motivation and free time)! (also, with different, fewer examples, and within legal-ish limits)

And I figured that one of the ways I could visualize a megajoule was by detonating a balloon filled with oxyhydrogen. But I feel like setting it off in the air and viewing with a drone may be cooler and possibly less disruptive than doing so on the ground. Of course, oxyhydrogen doesn't just explode when you ask it to. But I feel like my hobby-level background with electronics would help me out here. My plan, bear with me, is to use some random 8-pin SMD mcu and altitude sensor to short a small piece of metal across a tiny EDLC to bring it up to a high enough temperature to ignite the hydrogen. But, while I can design that while waiting for the stuff I ordered to arrive, I'd like to do so with some kind of weight constraint, if oxyhydrogen is lighter than air at all. Feedback on the ignition plan is also welcome.

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    $\begingroup$ I'm sorry, but having a megajoule of an explosive gas mixture nearby is NOT something you want to do (particularly since it can be set off by a static discharge). For example, stored energies of ~10 Joules are often considered hazardous in OSHA-relevant settings. A megajoule is asking to be a Darwin award winner, which one should not aspire to. $\endgroup$
    – Jon Custer
    Oct 27, 2022 at 19:17
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    $\begingroup$ Note: a pound of TNT is about 2 MJ. $\endgroup$
    – Jon Custer
    Oct 27, 2022 at 20:16
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    $\begingroup$ This is all to understand how big a joule is? $\endgroup$ Oct 27, 2022 at 20:39
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    $\begingroup$ This is a matter of simple calculation. If you don't know how to calculate it, then all this looks like just another reason not to anything like that. $\endgroup$
    – Mithoron
    Oct 27, 2022 at 20:41
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    $\begingroup$ You could eat a candy bar instead. It is interesting that four candy bars oxidized to $\ce{CO2}$ release as much energy as a kilogram of TNT exploding. It is all about the speed of releasing the energy, I guess. $\endgroup$
    – Karsten
    Oct 27, 2022 at 21:11

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Here is how to illustrate one or a few joules in a relatively sane manner.

Start with a large glass or clear plastic bowl, which you place on the floor in front of you. Now take a beaker and add some water to it, preferably with a dye to make things easier to see -- 100 mL for each joule you want to demonstrate. Then dump the water from waist level into the bowl. The "blast" energy when the water hits is roughly one joule per 100 mL of water.

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  • $\begingroup$ Thanks! For the megajoule thing I just ended up weighing out some wood pellets and burning them, then accelerated to 70 mph on a straight stretch of highway and slammed on the brakes. I am at once enlightened, very dizzy, and trying to rent a large passenger aircraft $\endgroup$
    – maximus
    Oct 28, 2022 at 0:27

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