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FRICTION FACTOR (f) *

Fluid Mechanics · FE Reference Handbook section

Fluid Mechanics
6 formulas
10 exam-style examples
~57 min
All Fluid Mechanics lectures

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.

Example 1
Friction factor (Darcy-Weisbach head loss) — solve for friction head loss — FRICTION FACTOR (f) *

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

  • Darcyfrictionfactor(f)=0.0490Darcy friction factor (f) = 0.0490
  • pipelength(L)=935.0mpipe length (L) = 935.0 m
  • pipediameter(D)=0.0500mpipe diameter (D) = 0.0500 m
  • velocity(V)=3.3500m/svelocity (V) = 3.3500 m/s
  • gravity(g)=9.8900m/s2gravity (g) = 9.8900 m/s^2

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.
D₁=150D₂=150Vf

Figure 1 — schematic for Friction factor (Darcy-Weisbach head loss) — solve for friction head loss — FRICTION FACTOR (f) *

Step-by-step solution

  1. Step 1 — State the governing relation:

    hf=fLDV22gh_f = f \dfrac{L}{D} \dfrac{V^2}{2g}
  2. Step 2 — Rearrange the relation so that h_f stands alone on the left-hand side.

  3. 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.

  4. Step 4 — Substitute the given values into the rearranged relation.

  5. Step 5 — Evaluate:

    hf=519.9 mh_{f} = 519.9\ \text{m}
  6. Step 6 — Check: returning h_f = 519.9 m to

    hf=fLDV22gh_f = f \dfrac{L}{D} \dfrac{V^2}{2g}

    reproduces the given quantities, and both sides carry the same units.

Answer:
hf=519.9 mh_{f} = 519.9\ \text{m}

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

Example 2
Friction factor (Darcy-Weisbach head loss) — solve for Darcy friction factor — FRICTION FACTOR (f) * (2)

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

  • pipelength(L)=130.0mpipe length (L) = 130.0 m
  • pipediameter(D)=0.1200mpipe diameter (D) = 0.1200 m
  • velocity(V)=2.4000m/svelocity (V) = 2.4000 m/s
  • gravity(g)=9.7300m/s2gravity (g) = 9.7300 m/s^2
  • frictionheadloss(hf)=8.1800mfriction head loss (h_f) = 8.1800 m

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.
D₁=150D₂=150Vf

Figure 2 — schematic for Friction factor (Darcy-Weisbach head loss) — solve for Darcy friction factor — FRICTION FACTOR (f) * (2)

Step-by-step solution

  1. Step 1 — State the governing relation:

    hf=fLDV22gh_f = f \dfrac{L}{D} \dfrac{V^2}{2g}
  2. Step 2 — Rearrange the relation so that f stands alone on the left-hand side.

  3. 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.

  4. Step 4 — Substitute the given values into the rearranged relation.

  5. Step 5 — Evaluate:

    f=0.0255f = 0.0255
  6. Step 6 — Check: returning f = 0.0255 to

    hf=fLDV22gh_f = f \dfrac{L}{D} \dfrac{V^2}{2g}

    reproduces the given quantities, and both sides carry the same units.

Answer:
f=0.0255f = 0.0255

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

Example 3
Friction factor (Darcy-Weisbach head loss) — solve for pipe length — FRICTION FACTOR (f) * (3)

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

  • Darcyfrictionfactor(f)=0.0380Darcy friction factor (f) = 0.0380
  • pipediameter(D)=0.2300mpipe diameter (D) = 0.2300 m
  • velocity(V)=3.1000m/svelocity (V) = 3.1000 m/s
  • gravity(g)=9.8900m/s2gravity (g) = 9.8900 m/s^2
  • frictionheadloss(hf)=5.1900mfriction head loss (h_f) = 5.1900 m

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.
D₁=150D₂=150Vf

Figure 3 — schematic for Friction factor (Darcy-Weisbach head loss) — solve for pipe length — FRICTION FACTOR (f) * (3)

Step-by-step solution

  1. Step 1 — State the governing relation:

    hf=fLDV22gh_f = f \dfrac{L}{D} \dfrac{V^2}{2g}
  2. Step 2 — Rearrange the relation so that L stands alone on the left-hand side.

  3. 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.

  4. Step 4 — Substitute the given values into the rearranged relation.

  5. Step 5 — Evaluate:

    L=64.6568 mL = 64.6568\ \text{m}
  6. Step 6 — Check: returning L = 64.6568 m to

    hf=fLDV22gh_f = f \dfrac{L}{D} \dfrac{V^2}{2g}

    reproduces the given quantities, and both sides carry the same units.

Answer:
L=64.6568 mL = 64.6568\ \text{m}

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

Example 4
Friction factor (Darcy-Weisbach head loss) — solve for friction head loss (case 2) — FRICTION FACTOR (f) * (4)

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

  • Darcyfrictionfactor(f)=0.0220Darcy friction factor (f) = 0.0220
  • pipelength(L)=665.0mpipe length (L) = 665.0 m
  • pipediameter(D)=0.3900mpipe diameter (D) = 0.3900 m
  • velocity(V)=1.9500m/svelocity (V) = 1.9500 m/s
  • gravity(g)=9.8300m/s2gravity (g) = 9.8300 m/s^2

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.
D₁=150D₂=150Vf

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

  1. Step 1 — State the governing relation:

    hf=fLDV22gh_f = f \dfrac{L}{D} \dfrac{V^2}{2g}
  2. Step 2 — Rearrange the relation so that h_f stands alone on the left-hand side.

  3. 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.

  4. Step 4 — Substitute the given values into the rearranged relation.

  5. Step 5 — Evaluate:

    hf=7.2555 mh_{f} = 7.2555\ \text{m}
  6. Step 6 — Check: returning h_f = 7.2555 m to

    hf=fLDV22gh_f = f \dfrac{L}{D} \dfrac{V^2}{2g}

    reproduces the given quantities, and both sides carry the same units.

Answer:
hf=7.2555 mh_{f} = 7.2555\ \text{m}

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

Example 5
Friction factor (Darcy-Weisbach head loss) — solve for Darcy friction factor (case 2) — FRICTION FACTOR (f) * (5)

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

  • pipelength(L)=360.0mpipe length (L) = 360.0 m
  • pipediameter(D)=0.4000mpipe diameter (D) = 0.4000 m
  • velocity(V)=1.0000m/svelocity (V) = 1.0000 m/s
  • gravity(g)=9.7900m/s2gravity (g) = 9.7900 m/s^2
  • frictionheadloss(hf)=19.1500mfriction head loss (h_f) = 19.1500 m

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.
D₁=150D₂=150Vf

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

  1. Step 1 — State the governing relation:

    hf=fLDV22gh_f = f \dfrac{L}{D} \dfrac{V^2}{2g}
  2. Step 2 — Rearrange the relation so that f stands alone on the left-hand side.

  3. 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.

  4. Step 4 — Substitute the given values into the rearranged relation.

  5. Step 5 — Evaluate:

    f=0.4166f = 0.4166
  6. Step 6 — Check: returning f = 0.4166 to

    hf=fLDV22gh_f = f \dfrac{L}{D} \dfrac{V^2}{2g}

    reproduces the given quantities, and both sides carry the same units.

Answer:
f=0.4166f = 0.4166

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

Example 6
Friction factor (Darcy-Weisbach head loss) — solve for pipe length (case 2) — FRICTION FACTOR (f) * (6)

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

  • Darcyfrictionfactor(f)=0.0240Darcy friction factor (f) = 0.0240
  • pipediameter(D)=0.2300mpipe diameter (D) = 0.2300 m
  • velocity(V)=1.7000m/svelocity (V) = 1.7000 m/s
  • gravity(g)=9.7800m/s2gravity (g) = 9.7800 m/s^2
  • frictionheadloss(hf)=2.1100mfriction head loss (h_f) = 2.1100 m

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.
D₁=150D₂=150Vf

Figure 6 — schematic for Friction factor (Darcy-Weisbach head loss) — solve for pipe length (case 2) — FRICTION FACTOR (f) * (6)

Step-by-step solution

  1. Step 1 — State the governing relation:

    hf=fLDV22gh_f = f \dfrac{L}{D} \dfrac{V^2}{2g}
  2. Step 2 — Rearrange the relation so that L stands alone on the left-hand side.

  3. 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.

  4. Step 4 — Substitute the given values into the rearranged relation.

  5. Step 5 — Evaluate:

    L=136.9 mL = 136.9\ \text{m}
  6. Step 6 — Check: returning L = 136.9 m to

    hf=fLDV22gh_f = f \dfrac{L}{D} \dfrac{V^2}{2g}

    reproduces the given quantities, and both sides carry the same units.

Answer:
L=136.9 mL = 136.9\ \text{m}

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

Example 7
Friction factor (Darcy-Weisbach head loss) — solve for friction head loss (case 3) — FRICTION FACTOR (f) * (7)

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

  • Darcyfrictionfactor(f)=0.0180Darcy friction factor (f) = 0.0180
  • pipelength(L)=520.0mpipe length (L) = 520.0 m
  • pipediameter(D)=0.2500mpipe diameter (D) = 0.2500 m
  • velocity(V)=3.9500m/svelocity (V) = 3.9500 m/s
  • gravity(g)=9.8000m/s2gravity (g) = 9.8000 m/s^2

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.
D₁=150D₂=150Vf

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

  1. Step 1 — State the governing relation:

    hf=fLDV22gh_f = f \dfrac{L}{D} \dfrac{V^2}{2g}
  2. Step 2 — Rearrange the relation so that h_f stands alone on the left-hand side.

  3. 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.

  4. Step 4 — Substitute the given values into the rearranged relation.

  5. Step 5 — Evaluate:

    hf=29.8040 mh_{f} = 29.8040\ \text{m}
  6. Step 6 — Check: returning h_f = 29.8040 m to

    hf=fLDV22gh_f = f \dfrac{L}{D} \dfrac{V^2}{2g}

    reproduces the given quantities, and both sides carry the same units.

Answer:
hf=29.8040 mh_{f} = 29.8040\ \text{m}

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

Example 8
Friction factor (Darcy-Weisbach head loss) — solve for Darcy friction factor (case 3) — FRICTION FACTOR (f) * (8)

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

  • pipelength(L)=530.0mpipe length (L) = 530.0 m
  • pipediameter(D)=0.4500mpipe diameter (D) = 0.4500 m
  • velocity(V)=1.4000m/svelocity (V) = 1.4000 m/s
  • gravity(g)=9.7200m/s2gravity (g) = 9.7200 m/s^2
  • frictionheadloss(hf)=13.8000mfriction head loss (h_f) = 13.8000 m

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.
D₁=150D₂=150Vf

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

  1. Step 1 — State the governing relation:

    hf=fLDV22gh_f = f \dfrac{L}{D} \dfrac{V^2}{2g}
  2. Step 2 — Rearrange the relation so that f stands alone on the left-hand side.

  3. 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.

  4. Step 4 — Substitute the given values into the rearranged relation.

  5. Step 5 — Evaluate:

    f=0.1162f = 0.1162
  6. Step 6 — Check: returning f = 0.1162 to

    hf=fLDV22gh_f = f \dfrac{L}{D} \dfrac{V^2}{2g}

    reproduces the given quantities, and both sides carry the same units.

Answer:
f=0.1162f = 0.1162

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

Example 9
Friction factor (Darcy-Weisbach head loss) — solve for pipe length (case 3) — FRICTION FACTOR (f) * (9)

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

  • Darcyfrictionfactor(f)=0.0200Darcy friction factor (f) = 0.0200
  • pipediameter(D)=0.5100mpipe diameter (D) = 0.5100 m
  • velocity(V)=1.2000m/svelocity (V) = 1.2000 m/s
  • gravity(g)=9.7400m/s2gravity (g) = 9.7400 m/s^2
  • frictionheadloss(hf)=18.0400mfriction head loss (h_f) = 18.0400 m

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.
D₁=150D₂=150Vf

Figure 9 — schematic for Friction factor (Darcy-Weisbach head loss) — solve for pipe length (case 3) — FRICTION FACTOR (f) * (9)

Step-by-step solution

  1. Step 1 — State the governing relation:

    hf=fLDV22gh_f = f \dfrac{L}{D} \dfrac{V^2}{2g}
  2. Step 2 — Rearrange the relation so that L stands alone on the left-hand side.

  3. 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.

  4. Step 4 — Substitute the given values into the rearranged relation.

  5. Step 5 — Evaluate:

    L=6223 mL = 6223\ \text{m}
  6. Step 6 — Check: returning L = 6,223 m to

    hf=fLDV22gh_f = f \dfrac{L}{D} \dfrac{V^2}{2g}

    reproduces the given quantities, and both sides carry the same units.

Answer:
L=6223 mL = 6223\ \text{m}

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

Example 10
Friction factor (Darcy-Weisbach head loss) — solve for friction head loss (case 4) — FRICTION FACTOR (f) * (10)

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

  • Darcyfrictionfactor(f)=0.0500Darcy friction factor (f) = 0.0500
  • pipelength(L)=945.0mpipe length (L) = 945.0 m
  • pipediameter(D)=0.0800mpipe diameter (D) = 0.0800 m
  • velocity(V)=2.6000m/svelocity (V) = 2.6000 m/s
  • gravity(g)=9.7300m/s2gravity (g) = 9.7300 m/s^2

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.
D₁=150D₂=150Vf

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

  1. Step 1 — State the governing relation:

    hf=fLDV22gh_f = f \dfrac{L}{D} \dfrac{V^2}{2g}
  2. Step 2 — Rearrange the relation so that h_f stands alone on the left-hand side.

  3. 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.

  4. Step 4 — Substitute the given values into the rearranged relation.

  5. Step 5 — Evaluate:

    hf=205.2 mh_{f} = 205.2\ \text{m}
  6. Step 6 — Check: returning h_f = 205.2 m to

    hf=fLDV22gh_f = f \dfrac{L}{D} \dfrac{V^2}{2g}

    reproduces the given quantities, and both sides carry the same units.

Answer:
hf=205.2 mh_{f} = 205.2\ \text{m}

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

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