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Please refer to page 6 of

http://www.physics.usyd.edu.au/ugrad/jphys/jphys_webct/jp_exams/1902_exam_2004.pdf [Broken]

I'm quoting from the solution guide:

http://www.physics.usyd.edu.au/ugrad/jphys/jphys_webct/jp_exams/1902_exam_solutions_2004.pdf [Broken]

[itex]P_1 = P_A + \rho g y_1 [/itex] and [itex]P_2 = P_A + \rho g y_2 [/itex]

Hence

[itex]\Delta h = y_1 - y_2[/itex].

Is it just me or does this last step total nonsense? AIUI, [itex]y_1[/itex] and [itex]y_2[/itex] refer to the position of the water levels measured with respect to two different coordinate systems. So how is it justified to say [itex]\Delta h = y_1 - y_2[/itex]? I drew a diagram and calculated the vertical separation between the water levels to be [itex]y_1 - y_2 + \frac{D_2 - D_1}{2}[/itex]. Could someone please point out if I am missing something obvious.

Thanks.

James

http://www.physics.usyd.edu.au/ugrad/jphys/jphys_webct/jp_exams/1902_exam_2004.pdf [Broken]

I'm quoting from the solution guide:

http://www.physics.usyd.edu.au/ugrad/jphys/jphys_webct/jp_exams/1902_exam_solutions_2004.pdf [Broken]

[itex]P_1 = P_A + \rho g y_1 [/itex] and [itex]P_2 = P_A + \rho g y_2 [/itex]

Hence

[itex]\Delta h = y_1 - y_2[/itex].

Is it just me or does this last step total nonsense? AIUI, [itex]y_1[/itex] and [itex]y_2[/itex] refer to the position of the water levels measured with respect to two different coordinate systems. So how is it justified to say [itex]\Delta h = y_1 - y_2[/itex]? I drew a diagram and calculated the vertical separation between the water levels to be [itex]y_1 - y_2 + \frac{D_2 - D_1}{2}[/itex]. Could someone please point out if I am missing something obvious.

Thanks.

James

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