Belt Friction
Statics · FE Reference Handbook section
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.
A statics problem uses Coulomb friction. Given friction coefficient (mu) = 0.6100; normal force (N) = 1,680 lb, determine the friction force (F) in lb.
Given
Find
friction force (F), in lb
Start with the thinking
- The governing relation printed in this handbook section is Coulomb friction.
- 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.
- Statics items reward recognising the unknown before touching a calculator.
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
Step 4 — Substitute the given values into the rearranged relation.
Step 5 — Evaluate:
Step 6 — Check: returning F = 1,025 lb to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 2,050 — kept a factor of two that cancels in the correct rearrangement.
- 512.4 — dropped that same factor in the other direction.
- 1,127 — rounded an intermediate value before the final step.
Reference: FE Reference Handbook — Statics → Belt Friction
A rope wrapped around a capstan uses belt friction to hold a load. Given slack side tension (T_2) = 104.0 lbf; coefficient of friction (mu) = 0.2500; wrap angle (beta) = 1.6500 rad, determine the tight side tension (T_1) in lbf.
Given
Find
tight side tension (T_1), in lbf
Start with the thinking
- The governing relation printed in this handbook section is Belt friction.
- Everything except T_1 is given, so isolate T_1 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.
- Belt friction relates the tight-side and slack-side tensions across a pulley through the coefficient of friction and wrap angle.
Figure 2 — schematic for Belt friction — solve for tight side tension — Belt Friction (2)
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for T_1:
Step 3 — List the givens: slack side tension (T_2) = 104.0 lbf, coefficient of friction (mu) = 0.2500, wrap angle (beta) = 1.6500 rad.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning T_1 = 157.1 lbf to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 314.2 — kept a factor of two that cancels in the correct rearrangement.
- 78.5507 — dropped that same factor in the other direction.
- 172.8 — rounded an intermediate value before the final step.
Reference: FE Handbook — Statics: Belt Friction
A statics problem uses Coulomb friction. Given normal force (N) = 1,496 lb; friction force (F) = 318.0 lb, determine the friction coefficient (mu).
Given
Find
friction coefficient (mu)
Start with the thinking
- The governing relation printed in this handbook section is Coulomb friction.
- Everything except mu is given, so isolate mu 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.
- Statics items reward recognising the unknown before touching a calculator.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange the relation so that mu stands alone on the left-hand side.
Step 3
Step 4 — Substitute the given values into the rearranged relation.
Step 5 — Evaluate:
Step 6 — Check: returning mu = 0.2126 to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 0.4251 — kept a factor of two that cancels in the correct rearrangement.
- 0.1063 — dropped that same factor in the other direction.
- 0.2338 — rounded an intermediate value before the final step.
Reference: FE Reference Handbook — Statics → Belt Friction
A conveyor belt's drive pulley is checked against belt friction slip criteria. Given coefficient of friction (mu) = 0.1300; wrap angle (beta) = 3.8000 rad; tight side tension (T_1) = 1,785 lbf, determine the slack side tension (T_2) in lbf.
Given
Find
slack side tension (T_2), in lbf
Start with the thinking
- The governing relation printed in this handbook section is Belt friction.
- Everything except T_2 is given, so isolate T_2 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.
- Belt friction relates the tight-side and slack-side tensions across a pulley through the coefficient of friction and wrap angle.
Figure 4 — schematic for Belt friction — solve for slack side tension — Belt Friction (4)
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for T_2:
Step 3 — List the givens: coefficient of friction (mu) = 0.1300, wrap angle (beta) = 3.8000 rad, tight side tension (T_1) = 1,785 lbf.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning T_2 = 1,089 lbf to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 2,178 — kept a factor of two that cancels in the correct rearrangement.
- 544.6 — dropped that same factor in the other direction.
- 1,198 — rounded an intermediate value before the final step.
Reference: FE Handbook — Statics: Belt Friction
A statics problem uses Coulomb friction. Given friction coefficient (mu) = 0.1500; friction force (F) = 367.0 lb, determine the normal force (N) in lb.
Given
Find
normal force (N), in lb
Start with the thinking
- The governing relation printed in this handbook section is Coulomb friction.
- Everything except N is given, so isolate N 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.
- Statics items reward recognising the unknown before touching a calculator.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange the relation so that N stands alone on the left-hand side.
Step 3
Step 4 — Substitute the given values into the rearranged relation.
Step 5 — Evaluate:
Step 6 — Check: returning N = 2,447 lb to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 4,893 — kept a factor of two that cancels in the correct rearrangement.
- 1,223 — dropped that same factor in the other direction.
- 2,691 — rounded an intermediate value before the final step.
Reference: FE Reference Handbook — Statics → Belt Friction
A flat belt drive on a pulley must not slip under belt friction limits. Given slack side tension (T_2) = 128.0 lbf; wrap angle (beta) = 2.9000 rad; tight side tension (T_1) = 1,975 lbf, determine the coefficient of friction (mu).
Given
Find
coefficient of friction (mu)
Start with the thinking
- The governing relation printed in this handbook section is Belt friction.
- Everything except mu is given, so isolate mu 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.
- Belt friction relates the tight-side and slack-side tensions across a pulley through the coefficient of friction and wrap angle.
Figure 6 — schematic for Belt friction — solve for coefficient of friction — Belt Friction (6)
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for mu:
Step 3 — List the givens: slack side tension (T_2) = 128.0 lbf, wrap angle (beta) = 2.9000 rad, tight side tension (T_1) = 1,975 lbf.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning mu = 0.9435 to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 1.8871 — kept a factor of two that cancels in the correct rearrangement.
- 0.4718 — dropped that same factor in the other direction.
- 1.0379 — rounded an intermediate value before the final step.
Reference: FE Handbook — Statics: Belt Friction
A statics problem uses Coulomb friction. Given friction coefficient (mu) = 0.2700; normal force (N) = 1,570 lb, determine the friction force (F) in lb.
Given
Find
friction force (F), in lb
Start with the thinking
- The governing relation printed in this handbook section is Coulomb friction.
- 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.
- Statics items reward recognising the unknown before touching a calculator.
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
Step 4 — Substitute the given values into the rearranged relation.
Step 5 — Evaluate:
Step 6 — Check: returning F = 423.9 lb to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 847.8 — kept a factor of two that cancels in the correct rearrangement.
- 212.0 — dropped that same factor in the other direction.
- 466.3 — rounded an intermediate value before the final step.
Reference: FE Reference Handbook — Statics → Belt Friction
A rope wrapped around a capstan uses belt friction to hold a load. Given slack side tension (T_2) = 68.0000 lbf; coefficient of friction (mu) = 0.4300; wrap angle (beta) = 2.9500 rad, determine the tight side tension (T_1) in lbf.
Given
Find
tight side tension (T_1), in lbf
Start with the thinking
- The governing relation printed in this handbook section is Belt friction.
- Everything except T_1 is given, so isolate T_1 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.
- Belt friction relates the tight-side and slack-side tensions across a pulley through the coefficient of friction and wrap angle.
Figure 8 — schematic for Belt friction — solve for tight side tension (case 2) — Belt Friction (8)
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for T_1:
Step 3 — List the givens: slack side tension (T_2) = 68.0000 lbf, coefficient of friction (mu) = 0.4300, wrap angle (beta) = 2.9500 rad.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning T_1 = 241.8 lbf to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 483.6 — kept a factor of two that cancels in the correct rearrangement.
- 120.9 — dropped that same factor in the other direction.
- 266.0 — rounded an intermediate value before the final step.
Reference: FE Handbook — Statics: Belt Friction
A statics problem uses Coulomb friction. Given normal force (N) = 922.0 lb; friction force (F) = 1,123 lb, determine the friction coefficient (mu).
Given
Find
friction coefficient (mu)
Start with the thinking
- The governing relation printed in this handbook section is Coulomb friction.
- Everything except mu is given, so isolate mu 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.
- Statics items reward recognising the unknown before touching a calculator.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange the relation so that mu stands alone on the left-hand side.
Step 3
Step 4 — Substitute the given values into the rearranged relation.
Step 5 — Evaluate:
Step 6 — Check: returning mu = 1.2180 to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 2.4360 — kept a factor of two that cancels in the correct rearrangement.
- 0.6090 — dropped that same factor in the other direction.
- 1.3398 — rounded an intermediate value before the final step.
Reference: FE Reference Handbook — Statics → Belt Friction
A conveyor belt's drive pulley is checked against belt friction slip criteria. Given coefficient of friction (mu) = 0.1700; wrap angle (beta) = 0.6000 rad; tight side tension (T_1) = 1,448 lbf, determine the slack side tension (T_2) in lbf.
Given
Find
slack side tension (T_2), in lbf
Start with the thinking
- The governing relation printed in this handbook section is Belt friction.
- Everything except T_2 is given, so isolate T_2 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.
- Belt friction relates the tight-side and slack-side tensions across a pulley through the coefficient of friction and wrap angle.
Figure 10 — schematic for Belt friction — solve for slack side tension (case 2) — Belt Friction (10)
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for T_2:
Step 3 — List the givens: coefficient of friction (mu) = 0.1700, wrap angle (beta) = 0.6000 rad, tight side tension (T_1) = 1,448 lbf.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning T_2 = 1,308 lbf to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 2,615 — kept a factor of two that cancels in the correct rearrangement.
- 653.8 — dropped that same factor in the other direction.
- 1,438 — rounded an intermediate value before the final step.
Reference: FE Handbook — Statics: Belt Friction