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How far will a homemade fire extinguisher shoot if we change the bottle size or the amount of baking soda?
Question Date: 2011-11-03
Answer 1:

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Answer 2:

It likely depends on the nozzle size as well as the bottle size and amount of baking soda (or whatever chemical is the extinguisher).The distance will depend on the pressure in the bottle, more reagent creates more gas per volume and more pressure, and the size of the orifice that the material comes out of, smaller means more velocity/distance think about putting your finger on a faucet. This change is described by Bernoulli's equation.

Another dramatic experiment take Mentos and drop them in a warm 2-L bottle of diet Coke and see what happens (stand back!). Then do the same experiment, only this time put a hole in the cap of the 2-Liter bottle and screw it back on very quickly after you drop the Mentos (can shoot up ~2-stories high w/ a hole about twice the size of a paper clip).


Answer 3:

This is a wonderful question and you should think long and hard about this! One thing you need to know is that the distance will be determined by two things: nozzle size and pressure in the bottle -at the time of opening-. That is, once you open the bottle you will have to be generating pressure at the rate it is released to maintain a steady stream at some size.

What does the amount of baking soda in the bottle change? A useful analogy is how does the amount of gas in your car affect its maximum speed (it doesn't)? Why is this?

This problem combines a number of important engineering principles: fuel supply, power generation (how fast you can generate force), and conservation laws (why does the size of the nozzle change the distance of the stream? Mass is conserved so how does the height of a fat cylinder change if you squeeze its radius smaller while keeping the volume constant?)



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