Specific gravity

Definition

Specific gravity is the ratio of the density of a substance to the density of a reference substance, typically water. It is a dimensionless quantity that indicates whether a material will sink or float in water.

5 Must Know Facts For Your Next Test

1. Specific gravity is calculated using the formula $SG = \frac{\rho_{substance}}{\rho_{water}}$, where $\rho$ represents density.
2. Since specific gravity is a ratio, it has no units and is therefore dimensionless.
3. A specific gravity greater than 1 means the substance is denser than water and will sink, while a specific gravity less than 1 means it is less dense and will float.
4. In fluid mechanics, specific gravity can help determine buoyant forces acting on submerged objects.
5. Temperature and pressure can affect specific gravity measurements because they influence the densities of both the substance and water.

Review Questions

• How do you calculate specific gravity?
• What does it mean if a material has a specific gravity less than 1?
• Why is specific gravity considered dimensionless?

Related terms

Density: Density is mass per unit volume, commonly represented by $\rho$, measured in kg/m^3.

Buoyant Force: The upward force exerted by a fluid that opposes the weight of an immersed object.

Archimedes' Principle: States that the buoyant force on an object submerged in fluid is equal to the weight of the fluid displaced by the object.