Equilibrium Requirements
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 10 m simply supported beam carries a 40 kN point load 3 m from A and a 12 kN/m uniform load over the full span. Find both reactions.
Given
Find
R_A and R_B
Start with the thinking
- Replace the distributed load with its resultant at midspan.
- Sum moments about A so R_A drops out of that equation.
Figure 1 — schematic for Reactions on a simply supported beam
Step-by-step solution
UDL resultant
Moments about A — ΣM_A = 0: R_B(10) = 40(3) + 120(5)
Right side — 120 + 600 = 720 kN·m
Reaction
Vertical equilibrium
Why the other options are there
- 80/80 kN (point load position ignored)
- R_A = 72, R_B = 88 (reactions swapped)
Reference: FE Reference Handbook — Statics — Equilibrium of rigid bodies
A statics problem uses Simply supported beam reaction. Given point load (P) = 35.5000 kip; load location (a) = 17.5000 ft; span (L) = 14.0000 ft, determine the far reaction (Rb) in kip.
Given
Find
far reaction (Rb), in kip
Start with the thinking
- The governing relation printed in this handbook section is Simply supported beam reaction.
- Everything except Rb is given, so isolate Rb 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 Rb stands alone on the left-hand side.
Step 3 — List the givens: point load (P) = 35.5000 kip, load location (a) = 17.5000 ft, span (L) = 14.0000 ft.
Step 4 — Substitute the given values into the rearranged relation.
Step 5 — Evaluate:
Step 6 — Check: returning Rb = 44.3750 kip to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 88.7500 — kept a factor of two that cancels in the correct rearrangement.
- 22.1875 — dropped that same factor in the other direction.
- 48.8125 — rounded an intermediate value before the final step.
Reference: FE Reference Handbook — Statics → Equilibrium Requirements
A statics problem uses Simply supported beam reaction. Given load location (a) = 4.0000 ft; span (L) = 16.0000 ft; far reaction (Rb) = 49.7400 kip, determine the point load (P) in kip.
Given
Find
point load (P), in kip
Start with the thinking
- The governing relation printed in this handbook section is Simply supported beam reaction.
- Everything except P is given, so isolate P 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 P 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 P = 199.0 kip to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 397.9 — kept a factor of two that cancels in the correct rearrangement.
- 99.4800 — dropped that same factor in the other direction.
- 218.9 — rounded an intermediate value before the final step.
Reference: FE Reference Handbook — Statics → Equilibrium Requirements
A statics problem uses Simply supported beam reaction. Given point load (P) = 44.5000 kip; span (L) = 34.0000 ft; far reaction (Rb) = 47.9400 kip, determine the load location (a) in ft.
Given
Find
load location (a), in ft
Start with the thinking
- The governing relation printed in this handbook section is Simply supported beam reaction.
- Everything except a is given, so isolate a 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 a 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 a = 36.6283 ft to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 73.2566 — kept a factor of two that cancels in the correct rearrangement.
- 18.3142 — dropped that same factor in the other direction.
- 40.2911 — rounded an intermediate value before the final step.
Reference: FE Reference Handbook — Statics → Equilibrium Requirements
A statics problem uses Simply supported beam reaction. Given point load (P) = 17.0000 kip; load location (a) = 14.0000 ft; far reaction (Rb) = 48.6700 kip, determine the span (L) in ft.
Given
Find
span (L), in ft
Start with the thinking
- The governing relation printed in this handbook section is Simply supported beam reaction.
- 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.
- 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 L stands alone on the left-hand side.
Step 3 — List the givens: point load (P) = 17.0000 kip, load location (a) = 14.0000 ft, far reaction (Rb) = 48.6700 kip.
Step 4 — Substitute the given values into the rearranged relation.
Step 5 — Evaluate:
Step 6 — Check: returning L = 4.8901 ft to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 9.7802 — kept a factor of two that cancels in the correct rearrangement.
- 2.4450 — dropped that same factor in the other direction.
- 5.3791 — rounded an intermediate value before the final step.
Reference: FE Reference Handbook — Statics → Equilibrium Requirements
A statics problem uses Simply supported beam reaction. Given point load (P) = 28.0000 kip; load location (a) = 4.0000 ft; span (L) = 22.0000 ft, determine the far reaction (Rb) in kip.
Given
Find
far reaction (Rb), in kip
Start with the thinking
- The governing relation printed in this handbook section is Simply supported beam reaction.
- Everything except Rb is given, so isolate Rb 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 Rb stands alone on the left-hand side.
Step 3 — List the givens: point load (P) = 28.0000 kip, load location (a) = 4.0000 ft, span (L) = 22.0000 ft.
Step 4 — Substitute the given values into the rearranged relation.
Step 5 — Evaluate:
Step 6 — Check: returning Rb = 5.0909 kip to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 10.1818 — kept a factor of two that cancels in the correct rearrangement.
- 2.5455 — dropped that same factor in the other direction.
- 5.6000 — rounded an intermediate value before the final step.
Reference: FE Reference Handbook — Statics → Equilibrium Requirements
A statics problem uses Simply supported beam reaction. Given load location (a) = 5.5000 ft; span (L) = 28.0000 ft; far reaction (Rb) = 9.8000 kip, determine the point load (P) in kip.
Given
Find
point load (P), in kip
Start with the thinking
- The governing relation printed in this handbook section is Simply supported beam reaction.
- Everything except P is given, so isolate P 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 P 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 P = 49.8909 kip to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 99.7818 — kept a factor of two that cancels in the correct rearrangement.
- 24.9455 — dropped that same factor in the other direction.
- 54.8800 — rounded an intermediate value before the final step.
Reference: FE Reference Handbook — Statics → Equilibrium Requirements
A statics problem uses Simply supported beam reaction. Given point load (P) = 27.5000 kip; span (L) = 33.0000 ft; far reaction (Rb) = 31.6700 kip, determine the load location (a) in ft.
Given
Find
load location (a), in ft
Start with the thinking
- The governing relation printed in this handbook section is Simply supported beam reaction.
- Everything except a is given, so isolate a 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 a 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 a = 38.0040 ft to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 76.0080 — kept a factor of two that cancels in the correct rearrangement.
- 19.0020 — dropped that same factor in the other direction.
- 41.8044 — rounded an intermediate value before the final step.
Reference: FE Reference Handbook — Statics → Equilibrium Requirements
A statics problem uses Simply supported beam reaction. Given point load (P) = 8.0000 kip; load location (a) = 7.5000 ft; far reaction (Rb) = 31.5200 kip, determine the span (L) in ft.
Given
Find
span (L), in ft
Start with the thinking
- The governing relation printed in this handbook section is Simply supported beam reaction.
- 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.
- 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 L stands alone on the left-hand side.
Step 3 — List the givens: point load (P) = 8.0000 kip, load location (a) = 7.5000 ft, far reaction (Rb) = 31.5200 kip.
Step 4 — Substitute the given values into the rearranged relation.
Step 5 — Evaluate:
Step 6 — Check: returning L = 1.9036 ft to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 3.8071 — kept a factor of two that cancels in the correct rearrangement.
- 0.9518 — dropped that same factor in the other direction.
- 2.0939 — rounded an intermediate value before the final step.
Reference: FE Reference Handbook — Statics → Equilibrium Requirements
A statics problem uses Simply supported beam reaction. Given point load (P) = 9.0000 kip; load location (a) = 3.0000 ft; span (L) = 24.0000 ft, determine the far reaction (Rb) in kip.
Given
Find
far reaction (Rb), in kip
Start with the thinking
- The governing relation printed in this handbook section is Simply supported beam reaction.
- Everything except Rb is given, so isolate Rb 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 Rb stands alone on the left-hand side.
Step 3 — List the givens: point load (P) = 9.0000 kip, load location (a) = 3.0000 ft, span (L) = 24.0000 ft.
Step 4 — Substitute the given values into the rearranged relation.
Step 5 — Evaluate:
Step 6 — Check: returning Rb = 1.1250 kip to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 2.2500 — kept a factor of two that cancels in the correct rearrangement.
- 0.5625 — dropped that same factor in the other direction.
- 1.2375 — rounded an intermediate value before the final step.
Reference: FE Reference Handbook — Statics → Equilibrium Requirements