Density
Environmental Engineering · FE Reference Handbook section
Handbook notes for this section
Definitions and conditions exactly as the handbook states them.
- The dry adiabatic lapse rate ΓAD is 0.98°C per 100 m (5.4°F per 1,000 ft). This is the rate at which dry air cools adiabatically
- The actual (environmental) lapse rate Γ is compared to ΓAD to determine stability as follows:
- Lapse Rate Stability Condition
- Surface Wind Solar Insolation Cloudinesse
- a. Surface wind speed is measured at 10 m above the ground.
- b. Corresponds to clear summer day with sun higher than 60° above the horizon.
- c. Corresponds to a summer day with a few broken clouds, or a clear day with sun 35-60° above the
- d. Corresponds to a fall afternoon, or a cloudy summer day, or clear summer day with the sun 15-35°.
Core formulas for this FE topic
Definitions, applicability, units, assumptions and worked examples for each relation.
Worked exam-style examples
The four ways this section is written on the real exam — thoughts first, then equations, then substitution.
density of a sludge sample measured in the laboratory Given mass (m) = 46.0000 kg; volume (V) = 0.5030 m^3, determine the density (rho) in kg/m^3.
Given
Find
density (rho), in kg/m^3
Start with the thinking
- The governing relation printed in this handbook section is Density.
- Everything except rho is given, so isolate rho symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- Density of a material sample is mass per unit volume, a fundamental property used throughout environmental engineering calculations.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for rho:
Step 3
Step 4 — Substitute the given values:
Step 5 — Evaluate:
\rho = 91.4513\ \text{kg/m^3}Step 6 — Check: returning rho = 91.4513 kg/m^3 to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 182.9 — kept a factor of two that cancels in the correct rearrangement.
- 45.7256 — dropped that same factor in the other direction.
- 100.6 — rounded an intermediate value before the final step.
Reference: FE Handbook — Density
density of a soil or waste material sample Given volume (V) = 0.9810 m^3; density (rho) = 1,639 kg/m^3, determine the mass (m) in kg.
Given
Find
mass (m), in kg
Start with the thinking
- The governing relation printed in this handbook section is Density.
- Everything except m is given, so isolate m symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- Density of a material sample is mass per unit volume, a fundamental property used throughout environmental engineering calculations.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for m:
Step 3
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning m = 1,608 kg to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 3,216 — kept a factor of two that cancels in the correct rearrangement.
- 803.9 — dropped that same factor in the other direction.
- 1,769 — rounded an intermediate value before the final step.
Reference: FE Handbook — Density
density calculation from measured mass and volume of a liquid sample Given mass (m) = 781.0 kg; density (rho) = 2,648 kg/m^3, determine the volume (V) in m^3.
Given
Find
volume (V), in m^3
Start with the thinking
- The governing relation printed in this handbook section is Density.
- Everything except V is given, so isolate V symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- Density of a material sample is mass per unit volume, a fundamental property used throughout environmental engineering calculations.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for V:
Step 3
Step 4 — Substitute the given values:
Step 5 — Evaluate:
V = 0.2949\ \text{m^3}Step 6 — Check: returning V = 0.2949 m^3 to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 0.5899 — kept a factor of two that cancels in the correct rearrangement.
- 0.1475 — dropped that same factor in the other direction.
- 0.3244 — rounded an intermediate value before the final step.
Reference: FE Handbook — Density
density of a sludge sample measured in the laboratory Given mass (m) = 346.0 kg; volume (V) = 0.2930 m^3, determine the density (rho) in kg/m^3.
Given
Find
density (rho), in kg/m^3
Start with the thinking
- The governing relation printed in this handbook section is Density.
- Everything except rho is given, so isolate rho symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- Density of a material sample is mass per unit volume, a fundamental property used throughout environmental engineering calculations.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for rho:
Step 3
Step 4 — Substitute the given values:
Step 5 — Evaluate:
\rho = 1181\ \text{kg/m^3}Step 6 — Check: returning rho = 1,181 kg/m^3 to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 2,362 — kept a factor of two that cancels in the correct rearrangement.
- 590.4 — dropped that same factor in the other direction.
- 1,299 — rounded an intermediate value before the final step.
Reference: FE Handbook — Density
density of a soil or waste material sample Given volume (V) = 0.9200 m^3; density (rho) = 701.0 kg/m^3, determine the mass (m) in kg.
Given
Find
mass (m), in kg
Start with the thinking
- The governing relation printed in this handbook section is Density.
- Everything except m is given, so isolate m symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- Density of a material sample is mass per unit volume, a fundamental property used throughout environmental engineering calculations.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for m:
Step 3
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning m = 644.9 kg to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 1,290 — kept a factor of two that cancels in the correct rearrangement.
- 322.5 — dropped that same factor in the other direction.
- 709.4 — rounded an intermediate value before the final step.
Reference: FE Handbook — Density
density calculation from measured mass and volume of a liquid sample Given mass (m) = 941.0 kg; density (rho) = 2,999 kg/m^3, determine the volume (V) in m^3.
Given
Find
volume (V), in m^3
Start with the thinking
- The governing relation printed in this handbook section is Density.
- Everything except V is given, so isolate V symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- Density of a material sample is mass per unit volume, a fundamental property used throughout environmental engineering calculations.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for V:
Step 3
Step 4 — Substitute the given values:
Step 5 — Evaluate:
V = 0.3138\ \text{m^3}Step 6 — Check: returning V = 0.3138 m^3 to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 0.6275 — kept a factor of two that cancels in the correct rearrangement.
- 0.1569 — dropped that same factor in the other direction.
- 0.3451 — rounded an intermediate value before the final step.
Reference: FE Handbook — Density
density of a sludge sample measured in the laboratory Given mass (m) = 903.0 kg; volume (V) = 0.5420 m^3, determine the density (rho) in kg/m^3.
Given
Find
density (rho), in kg/m^3
Start with the thinking
- The governing relation printed in this handbook section is Density.
- Everything except rho is given, so isolate rho symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- Density of a material sample is mass per unit volume, a fundamental property used throughout environmental engineering calculations.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for rho:
Step 3
Step 4 — Substitute the given values:
Step 5 — Evaluate:
\rho = 1666\ \text{kg/m^3}Step 6 — Check: returning rho = 1,666 kg/m^3 to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 3,332 — kept a factor of two that cancels in the correct rearrangement.
- 833.0 — dropped that same factor in the other direction.
- 1,833 — rounded an intermediate value before the final step.
Reference: FE Handbook — Density
density of a soil or waste material sample Given volume (V) = 0.7660 m^3; density (rho) = 920.0 kg/m^3, determine the mass (m) in kg.
Given
Find
mass (m), in kg
Start with the thinking
- The governing relation printed in this handbook section is Density.
- Everything except m is given, so isolate m symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- Density of a material sample is mass per unit volume, a fundamental property used throughout environmental engineering calculations.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for m:
Step 3
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning m = 704.7 kg to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 1,409 — kept a factor of two that cancels in the correct rearrangement.
- 352.4 — dropped that same factor in the other direction.
- 775.2 — rounded an intermediate value before the final step.
Reference: FE Handbook — Density
density calculation from measured mass and volume of a liquid sample Given mass (m) = 981.0 kg; density (rho) = 1,018 kg/m^3, determine the volume (V) in m^3.
Given
Find
volume (V), in m^3
Start with the thinking
- The governing relation printed in this handbook section is Density.
- Everything except V is given, so isolate V symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- Density of a material sample is mass per unit volume, a fundamental property used throughout environmental engineering calculations.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for V:
Step 3
Step 4 — Substitute the given values:
Step 5 — Evaluate:
V = 0.9637\ \text{m^3}Step 6 — Check: returning V = 0.9637 m^3 to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 1.9273 — kept a factor of two that cancels in the correct rearrangement.
- 0.4818 — dropped that same factor in the other direction.
- 1.0600 — rounded an intermediate value before the final step.
Reference: FE Handbook — Density
density of a sludge sample measured in the laboratory Given mass (m) = 376.0 kg; volume (V) = 0.1250 m^3, determine the density (rho) in kg/m^3.
Given
Find
density (rho), in kg/m^3
Start with the thinking
- The governing relation printed in this handbook section is Density.
- Everything except rho is given, so isolate rho symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- Density of a material sample is mass per unit volume, a fundamental property used throughout environmental engineering calculations.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for rho:
Step 3
Step 4 — Substitute the given values:
Step 5 — Evaluate:
\rho = 3008\ \text{kg/m^3}Step 6 — Check: returning rho = 3,008 kg/m^3 to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 6,016 — kept a factor of two that cancels in the correct rearrangement.
- 1,504 — dropped that same factor in the other direction.
- 3,309 — rounded an intermediate value before the final step.
Reference: FE Handbook — Density