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Zorluk: ZorFluids at Rest, Archimedes' Principle and Viscosity

A metallic sphere weighs 5.0 N5.0\text{ N} in air. When completely immersed in water, its apparent weight is 3.0 N3.0\text{ N}. When completely immersed in an unknown liquid XX, its apparent weight is 3.4 N3.4\text{ N}. What is the density of liquid XX in kg/m3\text{kg/m}^3? (Take the density of water as 1000 kg/m31000\text{ kg/m}^3 and acceleration due to gravity g=10 m/s2g = 10\text{ m/s}^2).

Cevap: 800 kg/m^3

Cevap

The density of liquid XX is 800 kg/m3800\text{ kg/m}^3.
The upthrust in water (2.0 N2.0\text{ N}) gives the volume of the sphere as 2.0×104 m32.0 \times 10^{-4}\text{ m}^3. Using the upthrust in liquid X (1.6 N1.6\text{ N}), the density of liquid X is calculated as ρX=1.6(2.0×104)(10)=800 kg/m3\rho_X = \frac{1.6}{(2.0 \times 10^{-4})(10)} = 800\text{ kg/m}^3.

Adım Adım Çözüm

1
Calculate upthrust in water
Uw=5.0 N3.0 N=2.0 NU_w = 5.0\text{ N} - 3.0\text{ N} = 2.0\text{ N}
Upthrust equals the loss in weight of the submerged body in water.
2
Determine the volume of the metallic sphere
V=Uwρwg=2.01000×10=2.0×104 m3V = \frac{U_w}{\rho_w g} = \frac{2.0}{1000 \times 10} = 2.0 \times 10^{-4}\text{ m}^3
According to Archimedes' principle, upthrust in water equals the weight of displaced water.
3
Calculate upthrust in liquid X
UX=5.0 N3.4 N=1.6 NU_X = 5.0\text{ N} - 3.4\text{ N} = 1.6\text{ N}
Loss of weight in liquid X gives the upthrust exerted by liquid X.
4
Calculate the density of liquid X
ρX=UXVg=1.6(2.0×104)×10=800 kg/m3\rho_X = \frac{U_X}{V g} = \frac{1.6}{(2.0 \times 10^{-4}) \times 10} = 800\text{ kg/m}^3
Rearranging UX=ρXVgU_X = \rho_X V g allows solving for the unknown fluid density.

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Archimedes' Principle and Apparent Weight
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