(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

Water is coming out of a water cannon at 25m/s, what is the pressure inside the cannon?

2. Relevant equations

Bernoulli's (modifiedd): v = √(2gh) -> h = v^2/2g

Prssure(liquid) : P = ρgh

3. The attempt at a solution

Well, I wasn't too sure how a water cannon works, so I "made one" that is just a giant vat with a lot of water, and a hole at the bottom.

I figured that for the water to come out at 25m/s, the height would have to be ~31m.

h = (25^2)/2g

So then I said, Pressure must be equal to ρgh, which is 1000 * 9.8 * 31m = 303,800Pa

But the answer the book gives says its "4.125 x 10^5 Pa absolute."

Any idea why my solution is incorrect?

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# Homework Help: Simple Pressure\Speed question

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