Explain why specific gravity is sometimes called relative de

Explain why specific gravity is sometimes called relative density.

What principle does the hydrometer depend on?

In this lab, which property will you measure directly with the hydrometer?

How would you use a hydrometer to determine the density and specific weight of a substance? What equations will you use? What assumptions will you make?

State the three forces acting on a sphere dropped in a liquid column.

State the equation used to determine the coefficient of viscosity of a falling sphere. Explain all terms of the equation.

Knowing the coefficient of viscosity, how would you determine the kinematic viscosity? State the equation.

Can a lab experiment be used to determine the coefficient of viscosity of oobleck? Why or why not?

Solution

Specific gravity is sometimes called relative density because it is the densiy of a material under consideration with respect to water. Specific gravity = density of substance/density of water at 4^oC. Since this is the density relative to water,it is also called relative density

Hydrometer uses Archimedes\' principle which states that a solid suspended in a fluid experienced a buoyant force which is equal to the weight of the liquid replaced by the solid

using hydrometer, relative density is measured off directly

After the relative density is known, multiplying it with 1000 gives density of fluid (in kg/m³) and multiplying it with 9800 gives unit weight of fluid(in N/m³)

The three forces acting on a sphere dropped in a liquid column are: weight of sphere, buoyant force and viscous drag force