Euler's Formula
Mechanics of Materials · FE Reference Handbook section
Handbook notes for this section
Definitions and conditions exactly as the handbook states them.
- Theoretical effective-length factors for columns include:
- Critical buckling stress for long columns:
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 mechanics of materials problem uses Euler buckling load. Given modulus (E) = 10,000 ksi; moment of inertia (I) = 110.0 in⁴; effective length factor (K) = 1.5000; unbraced length (L) = 98.0000 in, determine the critical load (Pcr) in kip.
Given
Find
critical load (Pcr), in kip
Start with the thinking
- The governing relation printed in this handbook section is Euler buckling load.
- Everything except Pcr is given, so isolate Pcr 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.
- Mechanics of Materials 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 Pcr stands alone on the left-hand side.
Step 3 — List the givens: modulus (E) = 10,000 ksi, moment of inertia (I) = 110.0 in⁴, effective length factor (K) = 1.5000, unbraced length (L) = 98.0000 in.
Step 4 — Substitute the given values into the rearranged relation.
Step 5 — Evaluate:
Step 6 — Check: returning Pcr = 502.4 kip to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 1,005 — kept a factor of two that cancels in the correct rearrangement.
- 251.2 — dropped that same factor in the other direction.
- 552.7 — rounded an intermediate value before the final step.
Reference: FE Reference Handbook — Mechanics of Materials → Euler's Formula
A mechanics of materials problem uses Euler buckling load. Given moment of inertia (I) = 130.0 in⁴; effective length factor (K) = 1.4000; unbraced length (L) = 196.0 in; critical load (Pcr) = 4,262 kip, determine the modulus (E) in ksi.
Given
Find
modulus (E), in ksi
Start with the thinking
- The governing relation printed in this handbook section is Euler buckling load.
- Everything except E is given, so isolate E 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.
- Mechanics of Materials 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 E stands alone on the left-hand side.
Step 3 — List the givens: moment of inertia (I) = 130.0 in⁴, effective length factor (K) = 1.4000, unbraced length (L) = 196.0 in, critical load (Pcr) = 4,262 kip.
Step 4 — Substitute the given values into the rearranged relation.
Step 5 — Evaluate:
Step 6 — Check: returning E = 250,114 ksi to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 500,229 — kept a factor of two that cancels in the correct rearrangement.
- 125,057 — dropped that same factor in the other direction.
- 275,126 — rounded an intermediate value before the final step.
Reference: FE Reference Handbook — Mechanics of Materials → Euler's Formula
A mechanics of materials problem uses Euler buckling load. Given modulus (E) = 12,000 ksi; effective length factor (K) = 1.0000; unbraced length (L) = 102.0 in; critical load (Pcr) = 4,724 kip, determine the moment of inertia (I) in in⁴.
Given
Find
moment of inertia (I), in in⁴
Start with the thinking
- The governing relation printed in this handbook section is Euler buckling load.
- Everything except I is given, so isolate I 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.
- Mechanics of Materials 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 I stands alone on the left-hand side.
Step 3 — List the givens: modulus (E) = 12,000 ksi, effective length factor (K) = 1.0000, unbraced length (L) = 102.0 in, critical load (Pcr) = 4,724 kip.
Step 4 — Substitute the given values into the rearranged relation.
Step 5 — Evaluate:
Step 6 — Check: returning I = 415.0 in⁴ to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 830.0 — kept a factor of two that cancels in the correct rearrangement.
- 207.5 — dropped that same factor in the other direction.
- 456.5 — rounded an intermediate value before the final step.
Reference: FE Reference Handbook — Mechanics of Materials → Euler's Formula
A mechanics of materials problem uses Euler buckling load. Given modulus (E) = 12,000 ksi; moment of inertia (I) = 45.0000 in⁴; effective length factor (K) = 1.0000; unbraced length (L) = 90.0000 in, determine the critical load (Pcr) in kip.
Given
Find
critical load (Pcr), in kip
Start with the thinking
- The governing relation printed in this handbook section is Euler buckling load.
- Everything except Pcr is given, so isolate Pcr 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.
- Mechanics of Materials 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 Pcr stands alone on the left-hand side.
Step 3 — List the givens: modulus (E) = 12,000 ksi, moment of inertia (I) = 45.0000 in⁴, effective length factor (K) = 1.0000, unbraced length (L) = 90.0000 in.
Step 4 — Substitute the given values into the rearranged relation.
Step 5 — Evaluate:
Step 6 — Check: returning Pcr = 658.0 kip to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 1,316 — kept a factor of two that cancels in the correct rearrangement.
- 329.0 — dropped that same factor in the other direction.
- 723.8 — rounded an intermediate value before the final step.
Reference: FE Reference Handbook — Mechanics of Materials → Euler's Formula
A mechanics of materials problem uses Euler buckling load. Given moment of inertia (I) = 265.0 in⁴; effective length factor (K) = 1.0000; unbraced length (L) = 208.0 in; critical load (Pcr) = 2,753 kip, determine the modulus (E) in ksi.
Given
Find
modulus (E), in ksi
Start with the thinking
- The governing relation printed in this handbook section is Euler buckling load.
- Everything except E is given, so isolate E 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.
- Mechanics of Materials 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 E stands alone on the left-hand side.
Step 3 — List the givens: moment of inertia (I) = 265.0 in⁴, effective length factor (K) = 1.0000, unbraced length (L) = 208.0 in, critical load (Pcr) = 2,753 kip.
Step 4 — Substitute the given values into the rearranged relation.
Step 5 — Evaluate:
Step 6 — Check: returning E = 45,539 ksi to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 91,079 — kept a factor of two that cancels in the correct rearrangement.
- 22,770 — dropped that same factor in the other direction.
- 50,093 — rounded an intermediate value before the final step.
Reference: FE Reference Handbook — Mechanics of Materials → Euler's Formula
A mechanics of materials problem uses Euler buckling load. Given modulus (E) = 20,000 ksi; effective length factor (K) = 0.7000; unbraced length (L) = 74.0000 in; critical load (Pcr) = 1,801 kip, determine the moment of inertia (I) in in⁴.
Given
Find
moment of inertia (I), in in⁴
Start with the thinking
- The governing relation printed in this handbook section is Euler buckling load.
- Everything except I is given, so isolate I 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.
- Mechanics of Materials 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 I stands alone on the left-hand side.
Step 3 — List the givens: modulus (E) = 20,000 ksi, effective length factor (K) = 0.7000, unbraced length (L) = 74.0000 in, critical load (Pcr) = 1,801 kip.
Step 4 — Substitute the given values into the rearranged relation.
Step 5 — Evaluate:
Step 6 — Check: returning I = 24.4818 in⁴ to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 48.9636 — kept a factor of two that cancels in the correct rearrangement.
- 12.2409 — dropped that same factor in the other direction.
- 26.9300 — rounded an intermediate value before the final step.
Reference: FE Reference Handbook — Mechanics of Materials → Euler's Formula
A mechanics of materials problem uses Euler buckling load. Given modulus (E) = 14,000 ksi; moment of inertia (I) = 300.0 in⁴; effective length factor (K) = 1.5000; unbraced length (L) = 177.0 in, determine the critical load (Pcr) in kip.
Given
Find
critical load (Pcr), in kip
Start with the thinking
- The governing relation printed in this handbook section is Euler buckling load.
- Everything except Pcr is given, so isolate Pcr 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.
- Mechanics of Materials 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 Pcr stands alone on the left-hand side.
Step 3 — List the givens: modulus (E) = 14,000 ksi, moment of inertia (I) = 300.0 in⁴, effective length factor (K) = 1.5000, unbraced length (L) = 177.0 in.
Step 4 — Substitute the given values into the rearranged relation.
Step 5 — Evaluate:
Step 6 — Check: returning Pcr = 588.1 kip to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 1,176 — kept a factor of two that cancels in the correct rearrangement.
- 294.0 — dropped that same factor in the other direction.
- 646.9 — rounded an intermediate value before the final step.
Reference: FE Reference Handbook — Mechanics of Materials → Euler's Formula
A mechanics of materials problem uses Euler buckling load. Given moment of inertia (I) = 150.0 in⁴; effective length factor (K) = 2.0000; unbraced length (L) = 95.0000 in; critical load (Pcr) = 2,226 kip, determine the modulus (E) in ksi.
Given
Find
modulus (E), in ksi
Start with the thinking
- The governing relation printed in this handbook section is Euler buckling load.
- Everything except E is given, so isolate E 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.
- Mechanics of Materials 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 E stands alone on the left-hand side.
Step 3 — List the givens: moment of inertia (I) = 150.0 in⁴, effective length factor (K) = 2.0000, unbraced length (L) = 95.0000 in, critical load (Pcr) = 2,226 kip.
Step 4 — Substitute the given values into the rearranged relation.
Step 5 — Evaluate:
Step 6 — Check: returning E = 54,280 ksi to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 108,560 — kept a factor of two that cancels in the correct rearrangement.
- 27,140 — dropped that same factor in the other direction.
- 59,708 — rounded an intermediate value before the final step.
Reference: FE Reference Handbook — Mechanics of Materials → Euler's Formula
A mechanics of materials problem uses Euler buckling load. Given modulus (E) = 10,000 ksi; effective length factor (K) = 0.7000; unbraced length (L) = 79.0000 in; critical load (Pcr) = 3,554 kip, determine the moment of inertia (I) in in⁴.
Given
Find
moment of inertia (I), in in⁴
Start with the thinking
- The governing relation printed in this handbook section is Euler buckling load.
- Everything except I is given, so isolate I 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.
- Mechanics of Materials 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 I stands alone on the left-hand side.
Step 3 — List the givens: modulus (E) = 10,000 ksi, effective length factor (K) = 0.7000, unbraced length (L) = 79.0000 in, critical load (Pcr) = 3,554 kip.
Step 4 — Substitute the given values into the rearranged relation.
Step 5 — Evaluate:
Step 6 — Check: returning I = 110.1 in⁴ to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 220.2 — kept a factor of two that cancels in the correct rearrangement.
- 55.0602 — dropped that same factor in the other direction.
- 121.1 — rounded an intermediate value before the final step.
Reference: FE Reference Handbook — Mechanics of Materials → Euler's Formula
A mechanics of materials problem uses Euler buckling load. Given modulus (E) = 18,000 ksi; moment of inertia (I) = 480.0 in⁴; effective length factor (K) = 1.8000; unbraced length (L) = 239.0 in, determine the critical load (Pcr) in kip.
Given
Find
critical load (Pcr), in kip
Start with the thinking
- The governing relation printed in this handbook section is Euler buckling load.
- Everything except Pcr is given, so isolate Pcr 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.
- Mechanics of Materials 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 Pcr stands alone on the left-hand side.
Step 3 — List the givens: modulus (E) = 18,000 ksi, moment of inertia (I) = 480.0 in⁴, effective length factor (K) = 1.8000, unbraced length (L) = 239.0 in.
Step 4 — Substitute the given values into the rearranged relation.
Step 5 — Evaluate:
Step 6 — Check: returning Pcr = 460.8 kip to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 921.5 — kept a factor of two that cancels in the correct rearrangement.
- 230.4 — dropped that same factor in the other direction.
- 506.8 — rounded an intermediate value before the final step.
Reference: FE Reference Handbook — Mechanics of Materials → Euler's Formula