# Help with physics resonance

1. Feb 15, 2006

### dekoi

There's a metal cylinder from which water is flowing out at a rate of 10^-6 m^3/s. A tuning fork of 300 Hz is placed on top of the cylinder. At what water levels will the first two resonance frequencies be heard?

It doesn't seem like a difficult problem, and it really isn't. I just can't seem to see it.

I dont think the flow rate has any signifiance in calculation; it's only useful to know that the water level is decreasing.

It's an open-closed system, so the natural frequencies are $$f_n = \frac{nv}{4L}$$ where n = 1, 3, 5, 7....

So in the first case, i think the first frequency heard would be 300 Hz. Hence, one can solve for $$L_1$$ to attain 0.286m. But how about for the next? Will it just be 3 times L_1 ? Or how do you solve for it otherwise?

Thanks
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Question 2: Is it logical to ask whether the beat frequency is e.g. +4 or -4? Afterall, $$f_{beat} = |f_2 - f_1|$$ so because of the absolute value,it is always +4.

Last edited by a moderator: Feb 15, 2006
2. Feb 16, 2006

### dekoi

Anyone?

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