Hooke's Law
Mechanics of Materials · FE Reference Handbook section
Handbook notes for this section
Definitions and conditions exactly as the handbook states them.
- When there is a temperature change from an initial temperature Ti to a final temperature Tf there are also thermally-induced
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 steel tension coupon obeys Hooke's law up to the yield point. Given modulus of elasticity (E) = 14,900 ksi; axial strain (epsilon) = 0.0002, determine the normal stress (sigma) in ksi.
Given
Find
normal stress (sigma), in ksi
Start with the thinking
- The governing relation printed in this handbook section is Hooke's law (axial).
- Everything except sigma is given, so isolate sigma 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.
- Hooke's law states that stress is proportional to strain within the elastic limit of the material.
Figure 1 — schematic for Hooke's law (axial) — solve for normal stress — Hooke's Law
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for sigma:
Step 3
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning sigma = 2.9800 ksi to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 5.9600 — kept a factor of two that cancels in the correct rearrangement.
- 1.4900 — dropped that same factor in the other direction.
- 3.2780 — rounded an intermediate value before the final step.
Reference: FE Handbook — Mechanics of Materials: Hooke's Law
An aluminum tie rod's elongation is predicted using Hooke's law. Given axial strain (epsilon) = 0.0014; normal stress (sigma) = 62.7000 ksi, determine the modulus of elasticity (E) in ksi.
Given
Find
modulus of elasticity (E), in ksi
Start with the thinking
- The governing relation printed in this handbook section is Hooke's law (axial).
- 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.
- Hooke's law states that stress is proportional to strain within the elastic limit of the material.
Figure 2 — schematic for Hooke's law (axial) — solve for modulus of elasticity — Hooke's Law (2)
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for E:
Step 3
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning E = 44,786 ksi to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 89,571 — kept a factor of two that cancels in the correct rearrangement.
- 22,393 — dropped that same factor in the other direction.
- 49,264 — rounded an intermediate value before the final step.
Reference: FE Handbook — Mechanics of Materials: Hooke's Law
A structural cable's stress-strain response follows Hooke's law under service load. Given modulus of elasticity (E) = 29,300 ksi; normal stress (sigma) = 23.6000 ksi, determine the axial strain (epsilon).
Given
Find
axial strain (epsilon)
Start with the thinking
- The governing relation printed in this handbook section is Hooke's law (axial).
- Everything except epsilon is given, so isolate epsilon 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.
- Hooke's law states that stress is proportional to strain within the elastic limit of the material.
Figure 3 — schematic for Hooke's law (axial) — solve for axial strain — Hooke's Law (3)
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for epsilon:
Step 3
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning epsilon = 0.0008 to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 0.0016 — kept a factor of two that cancels in the correct rearrangement.
- 0.0004 — dropped that same factor in the other direction.
- 0.0009 — rounded an intermediate value before the final step.
Reference: FE Handbook — Mechanics of Materials: Hooke's Law
A steel tension coupon obeys Hooke's law up to the yield point. Given modulus of elasticity (E) = 25,000 ksi; axial strain (epsilon) = 0.0020, determine the normal stress (sigma) in ksi.
Given
Find
normal stress (sigma), in ksi
Start with the thinking
- The governing relation printed in this handbook section is Hooke's law (axial).
- Everything except sigma is given, so isolate sigma 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.
- Hooke's law states that stress is proportional to strain within the elastic limit of the material.
Figure 4 — schematic for Hooke's law (axial) — solve for normal stress (case 2) — Hooke's Law (4)
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for sigma:
Step 3
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning sigma = 50.0000 ksi to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 100.0 — kept a factor of two that cancels in the correct rearrangement.
- 25.0000 — dropped that same factor in the other direction.
- 55.0000 — rounded an intermediate value before the final step.
Reference: FE Handbook — Mechanics of Materials: Hooke's Law
An aluminum tie rod's elongation is predicted using Hooke's law. Given axial strain (epsilon) = 0.0014; normal stress (sigma) = 75.3000 ksi, determine the modulus of elasticity (E) in ksi.
Given
Find
modulus of elasticity (E), in ksi
Start with the thinking
- The governing relation printed in this handbook section is Hooke's law (axial).
- 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.
- Hooke's law states that stress is proportional to strain within the elastic limit of the material.
Figure 5 — schematic for Hooke's law (axial) — solve for modulus of elasticity (case 2) — Hooke's Law (5)
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for E:
Step 3
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning E = 53,786 ksi to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 107,571 — kept a factor of two that cancels in the correct rearrangement.
- 26,893 — dropped that same factor in the other direction.
- 59,164 — rounded an intermediate value before the final step.
Reference: FE Handbook — Mechanics of Materials: Hooke's Law
A structural cable's stress-strain response follows Hooke's law under service load. Given modulus of elasticity (E) = 24,800 ksi; normal stress (sigma) = 56.4000 ksi, determine the axial strain (epsilon).
Given
Find
axial strain (epsilon)
Start with the thinking
- The governing relation printed in this handbook section is Hooke's law (axial).
- Everything except epsilon is given, so isolate epsilon 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.
- Hooke's law states that stress is proportional to strain within the elastic limit of the material.
Figure 6 — schematic for Hooke's law (axial) — solve for axial strain (case 2) — Hooke's Law (6)
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for epsilon:
Step 3
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning epsilon = 0.0023 to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 0.0045 — kept a factor of two that cancels in the correct rearrangement.
- 0.0011 — dropped that same factor in the other direction.
- 0.0025 — rounded an intermediate value before the final step.
Reference: FE Handbook — Mechanics of Materials: Hooke's Law
A steel tension coupon obeys Hooke's law up to the yield point. Given modulus of elasticity (E) = 19,100 ksi; axial strain (epsilon) = 0.0016, determine the normal stress (sigma) in ksi.
Given
Find
normal stress (sigma), in ksi
Start with the thinking
- The governing relation printed in this handbook section is Hooke's law (axial).
- Everything except sigma is given, so isolate sigma 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.
- Hooke's law states that stress is proportional to strain within the elastic limit of the material.
Figure 7 — schematic for Hooke's law (axial) — solve for normal stress (case 3) — Hooke's Law (7)
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for sigma:
Step 3
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning sigma = 30.5600 ksi to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 61.1200 — kept a factor of two that cancels in the correct rearrangement.
- 15.2800 — dropped that same factor in the other direction.
- 33.6160 — rounded an intermediate value before the final step.
Reference: FE Handbook — Mechanics of Materials: Hooke's Law
An aluminum tie rod's elongation is predicted using Hooke's law. Given axial strain (epsilon) = 0.0008; normal stress (sigma) = 80.0000 ksi, determine the modulus of elasticity (E) in ksi.
Given
Find
modulus of elasticity (E), in ksi
Start with the thinking
- The governing relation printed in this handbook section is Hooke's law (axial).
- 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.
- Hooke's law states that stress is proportional to strain within the elastic limit of the material.
Figure 8 — schematic for Hooke's law (axial) — solve for modulus of elasticity (case 3) — Hooke's Law (8)
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for E:
Step 3
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning E = 100,000 ksi to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 200,000 — kept a factor of two that cancels in the correct rearrangement.
- 50,000 — dropped that same factor in the other direction.
- 110,000 — rounded an intermediate value before the final step.
Reference: FE Handbook — Mechanics of Materials: Hooke's Law
A structural cable's stress-strain response follows Hooke's law under service load. Given modulus of elasticity (E) = 29,000 ksi; normal stress (sigma) = 54.9000 ksi, determine the axial strain (epsilon).
Given
Find
axial strain (epsilon)
Start with the thinking
- The governing relation printed in this handbook section is Hooke's law (axial).
- Everything except epsilon is given, so isolate epsilon 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.
- Hooke's law states that stress is proportional to strain within the elastic limit of the material.
Figure 9 — schematic for Hooke's law (axial) — solve for axial strain (case 3) — Hooke's Law (9)
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for epsilon:
Step 3
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning epsilon = 0.0019 to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 0.0038 — kept a factor of two that cancels in the correct rearrangement.
- 0.0009 — dropped that same factor in the other direction.
- 0.0021 — rounded an intermediate value before the final step.
Reference: FE Handbook — Mechanics of Materials: Hooke's Law
A steel tension coupon obeys Hooke's law up to the yield point. Given modulus of elasticity (E) = 13,000 ksi; axial strain (epsilon) = 0.0019, determine the normal stress (sigma) in ksi.
Given
Find
normal stress (sigma), in ksi
Start with the thinking
- The governing relation printed in this handbook section is Hooke's law (axial).
- Everything except sigma is given, so isolate sigma 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.
- Hooke's law states that stress is proportional to strain within the elastic limit of the material.
Figure 10 — schematic for Hooke's law (axial) — solve for normal stress (case 4) — Hooke's Law (10)
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for sigma:
Step 3
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning sigma = 24.7000 ksi to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 49.4000 — kept a factor of two that cancels in the correct rearrangement.
- 12.3500 — dropped that same factor in the other direction.
- 27.1700 — rounded an intermediate value before the final step.
Reference: FE Handbook — Mechanics of Materials: Hooke's Law