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Zorluk: OrtaFluids at Rest, Archimedes' Principle and Viscosity

A U-tube open at both ends contains mercury of density 13600 kg/m313\text{}600\text{ kg/m}^3. Water of density 1000 kg/m31000\text{ kg/m}^3 is poured into one arm until the water column reaches a height of 27.2 cm27.2\text{ cm}. What is the difference in height, in cm\text{cm}, between the mercury surfaces in the two arms?

Cevap: 2 cm

Cevap

The difference in height between the mercury surfaces in the two arms is 2.0 cm2.0\text{ cm}.
At the boundary level where water meets mercury, the pressure produced by the 27.2 cm27.2\text{ cm} water column must equal the pressure of the mercury column above that same horizontal level. Using hwρw=hmρmh_w \rho_w = h_m \rho_m, we solve for the mercury height difference: hm=27.2×100013600=2.0 cmh_m = \frac{27.2 \times 1000}{13600} = 2.0\text{ cm}.

Adım Adım Çözüm

1
Equate the hydrostatic pressure exerted by the water column to the hydrostatic pressure exerted by the balancing mercury column at the interface level.
hwρwg=hmρmgh_w \rho_w g = h_m \rho_m g
At the same horizontal level within a continuous fluid at rest, the pressures must be equal.
2
Cancel the acceleration due to gravity (gg) from both sides of the equation.
hwρw=hmρmh_w \rho_w = h_m \rho_m
Gravity acts equally on both liquid columns.
3
Substitute the known values (hw=27.2 cmh_w = 27.2\text{ cm}, ρw=1000 kg/m3\rho_w = 1000\text{ kg/m}^3, ρm=13600 kg/m3\rho_m = 13600\text{ kg/m}^3) into the pressure relation.
27.2×1000=hm×1360027.2 \times 1000 = h_m \times 13600
Inserting the physical quantities isolates the unknown mercury column height hmh_m.
4
Solve for the height difference hmh_m of the mercury levels.
hm=2720013600=2.0 cmh_m = \frac{27200}{13600} = 2.0\text{ cm}
Dividing the water pressure head product by the density of mercury yields the height of the mercury column.

Anahtar Kavram

Hydrostatic pressure equilibrium in immiscible fluids (U-tube manometer)
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