Question

Difficulty: MediumFluids at Rest, Archimedes' Principle and Viscosity

A solid alloy specimen weighs 240 g240\text{ g} in air, 180 g180\text{ g} when completely immersed in water, and 195 g195\text{ g} when completely immersed in an unknown liquid XX. What is the relative density of liquid XX?

  1. 0.750.75Answer
  2. B
    0.810.81
  3. C
    1.331.33
  4. D
    0.250.25

Answer

The relative density of liquid X is 0.750.75.
According to Archimedes' principle, relative density of a liquid is the ratio of the upthrust experienced by a solid in that liquid to the upthrust experienced by the same solid in water. Upthrust in water is 240 g180 g=60 g240\text{ g} - 180\text{ g} = 60\text{ g}, and upthrust in liquid X is 240 g195 g=45 g240\text{ g} - 195\text{ g} = 45\text{ g}. Dividing 4545 by 6060 gives 0.750.75.

Step-by-Step Solution

1
Calculate the upthrust in water
240 g180 g=60 g240\text{ g} - 180\text{ g} = 60\text{ g}
By Archimedes' principle, upthrust in water equals the mass loss when immersed in water.
2
Calculate the upthrust in liquid X
240 g195 g=45 g240\text{ g} - 195\text{ g} = 45\text{ g}
Upthrust in liquid X equals the mass loss when immersed in liquid X.
3
Determine the relative density of liquid X
\text{Relative Density} = \frac{\text{Upthrust in liquid X}}{\text{Upthrust in water}} = \frac{45\text{ g}}{60\text{ g}} = 0.75
Relative density of a liquid is defined as the ratio of the weight of a given volume of the liquid to the weight of an equal volume of water.

Key Concept

Archimedes' Principle and Relative Density of Liquids
Estimated Time:1m 30s
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