The shape of the water is that of a "spherical cap." The formula for the volume of a spherical cap is ...
... V = π·h²·(r -h/3) . . . . . . . from web search
For a radius of 5 in, this is
... V = π·h²·(5 -h/3) . . . . in³
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For h=0
... V = π·0²·(5 -0/3) = 0
For h=5 in
... V = π·(5 in)²·((5 -5/3) in) = (2/3)π·5³ in³ . . . . . the volume of a hemisphere of radius 5
