PROPERTIES OF FLUIDS: Different properties of fluids. (Fluid mechanics lesson 2)

Summary

This video explains the essential properties of fluids, including density, specific weight, specific volume, and specific gravity. It highlights that density is the ratio of mass to volume, with water's density being 1000 kg/m³. Specific weight is the ratio of weight to volume, and specific volume refers to the volume per unit mass of a fluid. Specific gravity, a dimensionless quantity, compares a fluid's density to water's density. The video aims to help viewers understand these concepts through simple explanations and encourages further learning through problem-solving in upcoming videos.

Takeaways

• 😀 Density is the ratio of the mass of a fluid to its volume, and is measured in kilograms per cubic meter.
• 😀 The density of liquids is generally considered constant, while the density of gases changes with pressure and temperature.
• 😀 Specific weight (or weight density) is the ratio of the weight of a fluid to its volume, and is calculated by multiplying the fluid's density by the acceleration due to gravity (g).
• 😀 The specific weight of water is approximately 9.81 × 1000 newtons per meter cubed.
• 😀 Specific volume is the volume occupied by a unit mass of fluid, and is the reciprocal of mass density.
• 😀 Specific volume is measured in cubic meters per kilogram.
• 😀 Specific gravity (or relative density) is the ratio of the weight density of a fluid to that of a standard fluid (water for liquids, air for gases).
• 😀 Specific gravity is a dimensionless quantity and is used to compare the densities of different fluids.
• 😀 The density of a liquid is equal to the specific gravity of the liquid multiplied by the density of water.
• 😀 In the next video, problems will be solved to further understand these fluid properties.

Q & A

What is the definition of density in the context of fluids?

Density, or mass density, is defined as the ratio of the mass of a fluid to its volume. It is mathematically expressed as mass per unit volume.

What is the unit of density in SI units?

The unit of density in SI units is kilograms per cubic meter (kg/m³).

How does the density of liquids and gases differ?

The density of liquids is typically constant, while the density of gases changes with changes in pressure and temperature.

What is specific weight, or weight density?

Specific weight, or weight density, is the ratio between the weight of a fluid and its volume. It is mathematically given by weight of the fluid divided by the volume of the fluid.

How is specific weight related to density?

Specific weight can be expressed as the product of the density (ρ) of a fluid and the acceleration due to gravity (g), i.e., specific weight = ρ × g.

What is the specific weight of water in SI units?

The specific weight of water in SI units is 9.81 × 1000 Newton per meter cubed (N/m³).

What is specific volume?

Specific volume is defined as the volume of a fluid occupied by a unit mass. It is the reciprocal of density, i.e., specific volume = 1 / density.

How is specific gravity defined?

Specific gravity is the ratio of the weight density of a fluid to the weight density of a standard fluid. For liquids, the standard fluid is water, and for gases, it is air.

What is the relationship between specific gravity and density?

Specific gravity can also be expressed as the ratio of the density of a fluid to the density of water, since weight density is proportional to density.

Why is specific gravity considered a dimensionless quantity?

Specific gravity is dimensionless because it is the ratio of two quantities with the same units, causing the units to cancel out.