Concept of Weight
Dynamics · 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 dynamics problem uses Constant-acceleration kinematics. Given initial velocity (v0) = 53.0000 ft/s; acceleration (a) = -16.5000 ft/s²; distance (s) = 306.0 ft, determine the final velocity (v) in ft/s.
Given
Find
final velocity (v), in ft/s
Start with the thinking
- The governing relation printed in this handbook section is Constant-acceleration kinematics.
- Everything except v is given, so isolate v 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.
- Dynamics 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 v stands alone on the left-hand side.
Step 3 — List the givens: initial velocity (v0) = 53.0000 ft/s, acceleration (a) = -16.5000 ft/s², distance (s) = 306.0 ft.
Step 4 — Substitute the given values into the rearranged relation.
Step 5 — Evaluate:
Step 6 — Check: returning v = 0.0000 ft/s to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 0.0000 — kept a factor of two that cancels in the correct rearrangement.
- 0.0000 — dropped that same factor in the other direction.
- 0.0000 — rounded an intermediate value before the final step.
Reference: FE Reference Handbook — Dynamics → Concept of Weight
A dynamics problem uses Constant-acceleration kinematics. Given initial velocity (v0) = 98.0000 ft/s; distance (s) = 398.0 ft; final velocity (v) = 119.2 ft/s, determine the acceleration (a) in ft/s².
Given
Find
acceleration (a), in ft/s²
Start with the thinking
- The governing relation printed in this handbook section is Constant-acceleration kinematics.
- 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.
- Dynamics 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 — List the givens: initial velocity (v0) = 98.0000 ft/s, distance (s) = 398.0 ft, final velocity (v) = 119.2 ft/s.
Step 4 — Substitute the given values into the rearranged relation.
Step 5 — Evaluate:
Step 6 — Check: returning a = 5.7847 ft/s² to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 11.5694 — kept a factor of two that cancels in the correct rearrangement.
- 2.8924 — dropped that same factor in the other direction.
- 6.3632 — rounded an intermediate value before the final step.
Reference: FE Reference Handbook — Dynamics → Concept of Weight
A dynamics problem uses Constant-acceleration kinematics. Given initial velocity (v0) = 37.0000 ft/s; acceleration (a) = 16.5000 ft/s²; final velocity (v) = 101.2 ft/s, determine the distance (s) in ft.
Given
Find
distance (s), in ft
Start with the thinking
- The governing relation printed in this handbook section is Constant-acceleration kinematics.
- Everything except s is given, so isolate s 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.
- Dynamics 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 s stands alone on the left-hand side.
Step 3 — List the givens: initial velocity (v0) = 37.0000 ft/s, acceleration (a) = 16.5000 ft/s², final velocity (v) = 101.2 ft/s.
Step 4 — Substitute the given values into the rearranged relation.
Step 5 — Evaluate:
Step 6 — Check: returning s = 268.9 ft to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 537.7 — kept a factor of two that cancels in the correct rearrangement.
- 134.4 — dropped that same factor in the other direction.
- 295.7 — rounded an intermediate value before the final step.
Reference: FE Reference Handbook — Dynamics → Concept of Weight
A dynamics problem uses Constant-acceleration kinematics. Given initial velocity (v0) = 77.0000 ft/s; acceleration (a) = -1.0000 ft/s²; distance (s) = 73.0000 ft, determine the final velocity (v) in ft/s.
Given
Find
final velocity (v), in ft/s
Start with the thinking
- The governing relation printed in this handbook section is Constant-acceleration kinematics.
- Everything except v is given, so isolate v 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.
- Dynamics 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 v stands alone on the left-hand side.
Step 3 — List the givens: initial velocity (v0) = 77.0000 ft/s, acceleration (a) = -1.0000 ft/s², distance (s) = 73.0000 ft.
Step 4 — Substitute the given values into the rearranged relation.
Step 5 — Evaluate:
Step 6 — Check: returning v = 76.0460 ft/s to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 152.1 — kept a factor of two that cancels in the correct rearrangement.
- 38.0230 — dropped that same factor in the other direction.
- 83.6506 — rounded an intermediate value before the final step.
Reference: FE Reference Handbook — Dynamics → Concept of Weight
A dynamics problem uses Constant-acceleration kinematics. Given initial velocity (v0) = 39.0000 ft/s; distance (s) = 158.0 ft; final velocity (v) = 79.8000 ft/s, determine the acceleration (a) in ft/s².
Given
Find
acceleration (a), in ft/s²
Start with the thinking
- The governing relation printed in this handbook section is Constant-acceleration kinematics.
- 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.
- Dynamics 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 — List the givens: initial velocity (v0) = 39.0000 ft/s, distance (s) = 158.0 ft, final velocity (v) = 79.8000 ft/s.
Step 4 — Substitute the given values into the rearranged relation.
Step 5 — Evaluate:
Step 6 — Check: returning a = 15.3387 ft/s² to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 30.6775 — kept a factor of two that cancels in the correct rearrangement.
- 7.6694 — dropped that same factor in the other direction.
- 16.8726 — rounded an intermediate value before the final step.
Reference: FE Reference Handbook — Dynamics → Concept of Weight
A dynamics problem uses Constant-acceleration kinematics. Given initial velocity (v0) = 94.0000 ft/s; acceleration (a) = -2.5000 ft/s²; final velocity (v) = 13.8000 ft/s, determine the distance (s) in ft.
Given
Find
distance (s), in ft
Start with the thinking
- The governing relation printed in this handbook section is Constant-acceleration kinematics.
- Everything except s is given, so isolate s 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.
- Dynamics 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 s stands alone on the left-hand side.
Step 3 — List the givens: initial velocity (v0) = 94.0000 ft/s, acceleration (a) = -2.5000 ft/s², final velocity (v) = 13.8000 ft/s.
Step 4 — Substitute the given values into the rearranged relation.
Step 5 — Evaluate:
Step 6 — Check: returning s = 1,729 ft to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 3,458 — kept a factor of two that cancels in the correct rearrangement.
- 864.6 — dropped that same factor in the other direction.
- 1,902 — rounded an intermediate value before the final step.
Reference: FE Reference Handbook — Dynamics → Concept of Weight
A dynamics problem uses Constant-acceleration kinematics. Given initial velocity (v0) = 96.0000 ft/s; acceleration (a) = 21.0000 ft/s²; distance (s) = 90.0000 ft, determine the final velocity (v) in ft/s.
Given
Find
final velocity (v), in ft/s
Start with the thinking
- The governing relation printed in this handbook section is Constant-acceleration kinematics.
- Everything except v is given, so isolate v 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.
- Dynamics 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 v stands alone on the left-hand side.
Step 3 — List the givens: initial velocity (v0) = 96.0000 ft/s, acceleration (a) = 21.0000 ft/s², distance (s) = 90.0000 ft.
Step 4 — Substitute the given values into the rearranged relation.
Step 5 — Evaluate:
Step 6 — Check: returning v = 114.0 ft/s to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 228.0 — kept a factor of two that cancels in the correct rearrangement.
- 57.0000 — dropped that same factor in the other direction.
- 125.4 — rounded an intermediate value before the final step.
Reference: FE Reference Handbook — Dynamics → Concept of Weight
A dynamics problem uses Constant-acceleration kinematics. Given initial velocity (v0) = 54.0000 ft/s; distance (s) = 166.0 ft; final velocity (v) = 18.9000 ft/s, determine the acceleration (a) in ft/s².
Given
Find
acceleration (a), in ft/s²
Start with the thinking
- The governing relation printed in this handbook section is Constant-acceleration kinematics.
- 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.
- Dynamics 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 — List the givens: initial velocity (v0) = 54.0000 ft/s, distance (s) = 166.0 ft, final velocity (v) = 18.9000 ft/s.
Step 4 — Substitute the given values into the rearranged relation.
Step 5 — Evaluate:
Step 6 — Check: returning a = -7.7072 ft/s² to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- -15.4144 — kept a factor of two that cancels in the correct rearrangement.
- -3.8536 — dropped that same factor in the other direction.
- -8.4779 — rounded an intermediate value before the final step.
Reference: FE Reference Handbook — Dynamics → Concept of Weight
A dynamics problem uses Constant-acceleration kinematics. Given initial velocity (v0) = 84.0000 ft/s; acceleration (a) = 12.0000 ft/s²; final velocity (v) = 100.6 ft/s, determine the distance (s) in ft.
Given
Find
distance (s), in ft
Start with the thinking
- The governing relation printed in this handbook section is Constant-acceleration kinematics.
- Everything except s is given, so isolate s 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.
- Dynamics 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 s stands alone on the left-hand side.
Step 3 — List the givens: initial velocity (v0) = 84.0000 ft/s, acceleration (a) = 12.0000 ft/s², final velocity (v) = 100.6 ft/s.
Step 4 — Substitute the given values into the rearranged relation.
Step 5 — Evaluate:
Step 6 — Check: returning s = 127.7 ft to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 255.4 — kept a factor of two that cancels in the correct rearrangement.
- 63.8408 — dropped that same factor in the other direction.
- 140.4 — rounded an intermediate value before the final step.
Reference: FE Reference Handbook — Dynamics → Concept of Weight
A dynamics problem uses Constant-acceleration kinematics. Given initial velocity (v0) = 87.0000 ft/s; acceleration (a) = -19.0000 ft/s²; distance (s) = 397.0 ft, determine the final velocity (v) in ft/s.
Given
Find
final velocity (v), in ft/s
Start with the thinking
- The governing relation printed in this handbook section is Constant-acceleration kinematics.
- Everything except v is given, so isolate v 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.
- Dynamics 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 v stands alone on the left-hand side.
Step 3 — List the givens: initial velocity (v0) = 87.0000 ft/s, acceleration (a) = -19.0000 ft/s², distance (s) = 397.0 ft.
Step 4 — Substitute the given values into the rearranged relation.
Step 5 — Evaluate:
Step 6 — Check: returning v = 0.0000 ft/s to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 0.0000 — kept a factor of two that cancels in the correct rearrangement.
- 0.0000 — dropped that same factor in the other direction.
- 0.0000 — rounded an intermediate value before the final step.
Reference: FE Reference Handbook — Dynamics → Concept of Weight