FRICTION FACTOR (f) *
Fluid Mechanics · FE Reference Handbook section
Handbook notes for this section
Definitions and conditions exactly as the handbook states them.
- * The Fanning Friction is this factor divided by 4.
- GLASS, DRAWN BRASS, COPPER, LEAD SMOOTH SMOOTH
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.
the friction factor for turbulent flow in a pipe from the Moody chart Given Darcy friction factor (f) = 0.0490; pipe length (L) = 935.0 m; pipe diameter (D) = 0.0500 m; velocity (V) = 3.3500 m/s; gravity (g) = 9.8900 m/s^2, determine the friction head loss (h_f) in m.
Given
Find
friction head loss (h_f), in m
Start with the thinking
- The governing relation printed in this handbook section is Friction factor (Darcy-Weisbach head loss).
- Everything except h_f is given, so isolate h_f 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.
- The Darcy friction factor governs head loss due to friction in a pipeline of a given length and diameter.
Figure 1 — schematic for Friction factor (Darcy-Weisbach head loss) — solve for friction head loss — FRICTION FACTOR (f) *
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange the relation so that h_f stands alone on the left-hand side.
Step 3 — List the givens: Darcy friction factor (f) = 0.0490, pipe length (L) = 935.0 m, pipe diameter (D) = 0.0500 m, velocity (V) = 3.3500 m/s, gravity (g) = 9.8900 m/s^2.
Step 4 — Substitute the given values into the rearranged relation.
Step 5 — Evaluate:
Step 6 — Check: returning h_f = 519.9 m to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 1,040 — kept a factor of two that cancels in the correct rearrangement.
- 259.9 — dropped that same factor in the other direction.
- 571.9 — rounded an intermediate value before the final step.
Reference: FE Handbook — Friction Factor
the friction factor used to compute head loss in a pipeline Given pipe length (L) = 130.0 m; pipe diameter (D) = 0.1200 m; velocity (V) = 2.4000 m/s; gravity (g) = 9.7300 m/s^2; friction head loss (h_f) = 8.1800 m, determine the Darcy friction factor (f).
Given
Find
Darcy friction factor (f)
Start with the thinking
- The governing relation printed in this handbook section is Friction factor (Darcy-Weisbach head loss).
- Everything except f is given, so isolate f 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.
- The Darcy friction factor governs head loss due to friction in a pipeline of a given length and diameter.
Figure 2 — schematic for Friction factor (Darcy-Weisbach head loss) — solve for Darcy friction factor — FRICTION FACTOR (f) * (2)
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange the relation so that f stands alone on the left-hand side.
Step 3 — List the givens: pipe length (L) = 130.0 m, pipe diameter (D) = 0.1200 m, velocity (V) = 2.4000 m/s, gravity (g) = 9.7300 m/s^2, friction head loss (h_f) = 8.1800 m.
Step 4 — Substitute the given values into the rearranged relation.
Step 5 — Evaluate:
Step 6 — Check: returning f = 0.0255 to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 0.0510 — kept a factor of two that cancels in the correct rearrangement.
- 0.0128 — dropped that same factor in the other direction.
- 0.0281 — rounded an intermediate value before the final step.
Reference: FE Handbook — Friction Factor
the friction factor for a rough concrete pipe carrying water Given Darcy friction factor (f) = 0.0380; pipe diameter (D) = 0.2300 m; velocity (V) = 3.1000 m/s; gravity (g) = 9.8900 m/s^2; friction head loss (h_f) = 5.1900 m, determine the pipe length (L) in m.
Given
Find
pipe length (L), in m
Start with the thinking
- The governing relation printed in this handbook section is Friction factor (Darcy-Weisbach head loss).
- Everything except L is given, so isolate L 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.
- The Darcy friction factor governs head loss due to friction in a pipeline of a given length and diameter.
Figure 3 — schematic for Friction factor (Darcy-Weisbach head loss) — solve for pipe length — FRICTION FACTOR (f) * (3)
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange the relation so that L stands alone on the left-hand side.
Step 3 — List the givens: Darcy friction factor (f) = 0.0380, pipe diameter (D) = 0.2300 m, velocity (V) = 3.1000 m/s, gravity (g) = 9.8900 m/s^2, friction head loss (h_f) = 5.1900 m.
Step 4 — Substitute the given values into the rearranged relation.
Step 5 — Evaluate:
Step 6 — Check: returning L = 64.6568 m to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 129.3 — kept a factor of two that cancels in the correct rearrangement.
- 32.3284 — dropped that same factor in the other direction.
- 71.1225 — rounded an intermediate value before the final step.
Reference: FE Handbook — Friction Factor
the friction factor for turbulent flow in a pipe from the Moody chart Given Darcy friction factor (f) = 0.0220; pipe length (L) = 665.0 m; pipe diameter (D) = 0.3900 m; velocity (V) = 1.9500 m/s; gravity (g) = 9.8300 m/s^2, determine the friction head loss (h_f) in m.
Given
Find
friction head loss (h_f), in m
Start with the thinking
- The governing relation printed in this handbook section is Friction factor (Darcy-Weisbach head loss).
- Everything except h_f is given, so isolate h_f 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.
- The Darcy friction factor governs head loss due to friction in a pipeline of a given length and diameter.
Figure 4 — schematic for Friction factor (Darcy-Weisbach head loss) — solve for friction head loss (case 2) — FRICTION FACTOR (f) * (4)
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange the relation so that h_f stands alone on the left-hand side.
Step 3 — List the givens: Darcy friction factor (f) = 0.0220, pipe length (L) = 665.0 m, pipe diameter (D) = 0.3900 m, velocity (V) = 1.9500 m/s, gravity (g) = 9.8300 m/s^2.
Step 4 — Substitute the given values into the rearranged relation.
Step 5 — Evaluate:
Step 6 — Check: returning h_f = 7.2555 m to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 14.5109 — kept a factor of two that cancels in the correct rearrangement.
- 3.6277 — dropped that same factor in the other direction.
- 7.9810 — rounded an intermediate value before the final step.
Reference: FE Handbook — Friction Factor
the friction factor used to compute head loss in a pipeline Given pipe length (L) = 360.0 m; pipe diameter (D) = 0.4000 m; velocity (V) = 1.0000 m/s; gravity (g) = 9.7900 m/s^2; friction head loss (h_f) = 19.1500 m, determine the Darcy friction factor (f).
Given
Find
Darcy friction factor (f)
Start with the thinking
- The governing relation printed in this handbook section is Friction factor (Darcy-Weisbach head loss).
- Everything except f is given, so isolate f 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.
- The Darcy friction factor governs head loss due to friction in a pipeline of a given length and diameter.
Figure 5 — schematic for Friction factor (Darcy-Weisbach head loss) — solve for Darcy friction factor (case 2) — FRICTION FACTOR (f) * (5)
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange the relation so that f stands alone on the left-hand side.
Step 3 — List the givens: pipe length (L) = 360.0 m, pipe diameter (D) = 0.4000 m, velocity (V) = 1.0000 m/s, gravity (g) = 9.7900 m/s^2, friction head loss (h_f) = 19.1500 m.
Step 4 — Substitute the given values into the rearranged relation.
Step 5 — Evaluate:
Step 6 — Check: returning f = 0.4166 to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 0.8332 — kept a factor of two that cancels in the correct rearrangement.
- 0.2083 — dropped that same factor in the other direction.
- 0.4583 — rounded an intermediate value before the final step.
Reference: FE Handbook — Friction Factor
the friction factor for a rough concrete pipe carrying water Given Darcy friction factor (f) = 0.0240; pipe diameter (D) = 0.2300 m; velocity (V) = 1.7000 m/s; gravity (g) = 9.7800 m/s^2; friction head loss (h_f) = 2.1100 m, determine the pipe length (L) in m.
Given
Find
pipe length (L), in m
Start with the thinking
- The governing relation printed in this handbook section is Friction factor (Darcy-Weisbach head loss).
- Everything except L is given, so isolate L 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.
- The Darcy friction factor governs head loss due to friction in a pipeline of a given length and diameter.
Figure 6 — schematic for Friction factor (Darcy-Weisbach head loss) — solve for pipe length (case 2) — FRICTION FACTOR (f) * (6)
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange the relation so that L stands alone on the left-hand side.
Step 3 — List the givens: Darcy friction factor (f) = 0.0240, pipe diameter (D) = 0.2300 m, velocity (V) = 1.7000 m/s, gravity (g) = 9.7800 m/s^2, friction head loss (h_f) = 2.1100 m.
Step 4 — Substitute the given values into the rearranged relation.
Step 5 — Evaluate:
Step 6 — Check: returning L = 136.9 m to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 273.7 — kept a factor of two that cancels in the correct rearrangement.
- 68.4290 — dropped that same factor in the other direction.
- 150.5 — rounded an intermediate value before the final step.
Reference: FE Handbook — Friction Factor
the friction factor for turbulent flow in a pipe from the Moody chart Given Darcy friction factor (f) = 0.0180; pipe length (L) = 520.0 m; pipe diameter (D) = 0.2500 m; velocity (V) = 3.9500 m/s; gravity (g) = 9.8000 m/s^2, determine the friction head loss (h_f) in m.
Given
Find
friction head loss (h_f), in m
Start with the thinking
- The governing relation printed in this handbook section is Friction factor (Darcy-Weisbach head loss).
- Everything except h_f is given, so isolate h_f 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.
- The Darcy friction factor governs head loss due to friction in a pipeline of a given length and diameter.
Figure 7 — schematic for Friction factor (Darcy-Weisbach head loss) — solve for friction head loss (case 3) — FRICTION FACTOR (f) * (7)
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange the relation so that h_f stands alone on the left-hand side.
Step 3 — List the givens: Darcy friction factor (f) = 0.0180, pipe length (L) = 520.0 m, pipe diameter (D) = 0.2500 m, velocity (V) = 3.9500 m/s, gravity (g) = 9.8000 m/s^2.
Step 4 — Substitute the given values into the rearranged relation.
Step 5 — Evaluate:
Step 6 — Check: returning h_f = 29.8040 m to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 59.6079 — kept a factor of two that cancels in the correct rearrangement.
- 14.9020 — dropped that same factor in the other direction.
- 32.7844 — rounded an intermediate value before the final step.
Reference: FE Handbook — Friction Factor
the friction factor used to compute head loss in a pipeline Given pipe length (L) = 530.0 m; pipe diameter (D) = 0.4500 m; velocity (V) = 1.4000 m/s; gravity (g) = 9.7200 m/s^2; friction head loss (h_f) = 13.8000 m, determine the Darcy friction factor (f).
Given
Find
Darcy friction factor (f)
Start with the thinking
- The governing relation printed in this handbook section is Friction factor (Darcy-Weisbach head loss).
- Everything except f is given, so isolate f 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.
- The Darcy friction factor governs head loss due to friction in a pipeline of a given length and diameter.
Figure 8 — schematic for Friction factor (Darcy-Weisbach head loss) — solve for Darcy friction factor (case 3) — FRICTION FACTOR (f) * (8)
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange the relation so that f stands alone on the left-hand side.
Step 3 — List the givens: pipe length (L) = 530.0 m, pipe diameter (D) = 0.4500 m, velocity (V) = 1.4000 m/s, gravity (g) = 9.7200 m/s^2, friction head loss (h_f) = 13.8000 m.
Step 4 — Substitute the given values into the rearranged relation.
Step 5 — Evaluate:
Step 6 — Check: returning f = 0.1162 to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 0.2324 — kept a factor of two that cancels in the correct rearrangement.
- 0.0581 — dropped that same factor in the other direction.
- 0.1278 — rounded an intermediate value before the final step.
Reference: FE Handbook — Friction Factor
the friction factor for a rough concrete pipe carrying water Given Darcy friction factor (f) = 0.0200; pipe diameter (D) = 0.5100 m; velocity (V) = 1.2000 m/s; gravity (g) = 9.7400 m/s^2; friction head loss (h_f) = 18.0400 m, determine the pipe length (L) in m.
Given
Find
pipe length (L), in m
Start with the thinking
- The governing relation printed in this handbook section is Friction factor (Darcy-Weisbach head loss).
- Everything except L is given, so isolate L 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.
- The Darcy friction factor governs head loss due to friction in a pipeline of a given length and diameter.
Figure 9 — schematic for Friction factor (Darcy-Weisbach head loss) — solve for pipe length (case 3) — FRICTION FACTOR (f) * (9)
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange the relation so that L stands alone on the left-hand side.
Step 3 — List the givens: Darcy friction factor (f) = 0.0200, pipe diameter (D) = 0.5100 m, velocity (V) = 1.2000 m/s, gravity (g) = 9.7400 m/s^2, friction head loss (h_f) = 18.0400 m.
Step 4 — Substitute the given values into the rearranged relation.
Step 5 — Evaluate:
Step 6 — Check: returning L = 6,223 m to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 12,446 — kept a factor of two that cancels in the correct rearrangement.
- 3,112 — dropped that same factor in the other direction.
- 6,845 — rounded an intermediate value before the final step.
Reference: FE Handbook — Friction Factor
the friction factor for turbulent flow in a pipe from the Moody chart Given Darcy friction factor (f) = 0.0500; pipe length (L) = 945.0 m; pipe diameter (D) = 0.0800 m; velocity (V) = 2.6000 m/s; gravity (g) = 9.7300 m/s^2, determine the friction head loss (h_f) in m.
Given
Find
friction head loss (h_f), in m
Start with the thinking
- The governing relation printed in this handbook section is Friction factor (Darcy-Weisbach head loss).
- Everything except h_f is given, so isolate h_f 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.
- The Darcy friction factor governs head loss due to friction in a pipeline of a given length and diameter.
Figure 10 — schematic for Friction factor (Darcy-Weisbach head loss) — solve for friction head loss (case 4) — FRICTION FACTOR (f) * (10)
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange the relation so that h_f stands alone on the left-hand side.
Step 3 — List the givens: Darcy friction factor (f) = 0.0500, pipe length (L) = 945.0 m, pipe diameter (D) = 0.0800 m, velocity (V) = 2.6000 m/s, gravity (g) = 9.7300 m/s^2.
Step 4 — Substitute the given values into the rearranged relation.
Step 5 — Evaluate:
Step 6 — Check: returning h_f = 205.2 m to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 410.3 — kept a factor of two that cancels in the correct rearrangement.
- 102.6 — dropped that same factor in the other direction.
- 225.7 — rounded an intermediate value before the final step.
Reference: FE Handbook — Friction Factor