Euler's Equation
Fluid Mechanics · FE Reference Handbook section
Handbook notes for this section
Definitions and conditions exactly as the handbook states them.
- For unsteady flow due to local acceleration (i.e., temporal acceleration) in the x-direction, the change in pressure between two
- points in a fluid can be determined by Euler's equation:
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.
Euler's equation applied along a streamline in an accelerating flow Given fluid density (rho) = 830.0 kg/m^3; velocity (V) = 4.6000 m/s; velocity differential (dV) = -0.1400 m/s; elevation differential (dz) = 0.7500 m; gravity (g) = 9.7600 m/s^2, determine the pressure differential (dp) in Pa.
Given
Find
pressure differential (dp), in Pa
Start with the thinking
- The governing relation printed in this handbook section is Euler's equation.
- Everything except dp is given, so isolate dp 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.
- Euler's equation for inviscid flow along a streamline underlies derivation of the Bernoulli equation.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange the relation so that dp stands alone on the left-hand side.
Step 3 — List the givens: fluid density (rho) = 830.0 kg/m^3, velocity (V) = 4.6000 m/s, velocity differential (dV) = -0.1400 m/s, elevation differential (dz) = 0.7500 m, gravity (g) = 9.7600 m/s^2.
Step 4 — Substitute the given values into the rearranged relation.
Step 5 — Evaluate:
Step 6 — Check: returning dp = -5,541 Pa to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- -11,082 — kept a factor of two that cancels in the correct rearrangement.
- -2,771 — dropped that same factor in the other direction.
- -6,095 — rounded an intermediate value before the final step.
Reference: FE Handbook — Euler's Equation
Euler's equation for a fluid particle in a converging nozzle Given pressure differential (dp) = 840.0 Pa; fluid density (rho) = 870.0 kg/m^3; velocity (V) = 3.9000 m/s; elevation differential (dz) = -0.5000 m; gravity (g) = 9.8900 m/s^2, determine the velocity differential (dV) in m/s.
Given
Find
velocity differential (dV), in m/s
Start with the thinking
- The governing relation printed in this handbook section is Euler's equation.
- Everything except dV is given, so isolate dV 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.
- Euler's equation for inviscid flow along a streamline underlies derivation of the Bernoulli equation.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange the relation so that dV stands alone on the left-hand side.
Step 3 — List the givens: pressure differential (dp) = 840.0 Pa, fluid density (rho) = 870.0 kg/m^3, velocity (V) = 3.9000 m/s, elevation differential (dz) = -0.5000 m, gravity (g) = 9.8900 m/s^2.
Step 4 — Substitute the given values into the rearranged relation.
Step 5 — Evaluate:
Step 6 — Check: returning dV = 1.0204 m/s to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 2.0408 — kept a factor of two that cancels in the correct rearrangement.
- 0.5102 — dropped that same factor in the other direction.
- 1.1224 — rounded an intermediate value before the final step.
Reference: FE Handbook — Euler's Equation
Euler's equation used to derive pressure change along a pipeline Given pressure differential (dp) = -4,250 Pa; fluid density (rho) = 1,040 kg/m^3; velocity (V) = 1.8000 m/s; velocity differential (dV) = -0.3200 m/s; gravity (g) = 9.8800 m/s^2, determine the elevation differential (dz) in m.
Given
Find
elevation differential (dz), in m
Start with the thinking
- The governing relation printed in this handbook section is Euler's equation.
- Everything except dz is given, so isolate dz 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.
- Euler's equation for inviscid flow along a streamline underlies derivation of the Bernoulli equation.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange the relation so that dz stands alone on the left-hand side.
Step 3 — List the givens: pressure differential (dp) = -4,250 Pa, fluid density (rho) = 1,040 kg/m^3, velocity (V) = 1.8000 m/s, velocity differential (dV) = -0.3200 m/s, gravity (g) = 9.8800 m/s^2.
Step 4 — Substitute the given values into the rearranged relation.
Step 5 — Evaluate:
Step 6 — Check: returning dz = 0.4719 m to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 0.9438 — kept a factor of two that cancels in the correct rearrangement.
- 0.2360 — dropped that same factor in the other direction.
- 0.5191 — rounded an intermediate value before the final step.
Reference: FE Handbook — Euler's Equation
Euler's equation applied along a streamline in an accelerating flow Given fluid density (rho) = 840.0 kg/m^3; velocity (V) = 2.1000 m/s; velocity differential (dV) = 0.1600 m/s; elevation differential (dz) = -0.0500 m; gravity (g) = 9.8500 m/s^2, determine the pressure differential (dp) in Pa.
Given
Find
pressure differential (dp), in Pa
Start with the thinking
- The governing relation printed in this handbook section is Euler's equation.
- Everything except dp is given, so isolate dp 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.
- Euler's equation for inviscid flow along a streamline underlies derivation of the Bernoulli equation.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange the relation so that dp stands alone on the left-hand side.
Step 3 — List the givens: fluid density (rho) = 840.0 kg/m^3, velocity (V) = 2.1000 m/s, velocity differential (dV) = 0.1600 m/s, elevation differential (dz) = -0.0500 m, gravity (g) = 9.8500 m/s^2.
Step 4 — Substitute the given values into the rearranged relation.
Step 5 — Evaluate:
Step 6 — Check: returning dp = 131.5 Pa to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 262.9 — kept a factor of two that cancels in the correct rearrangement.
- 65.7300 — dropped that same factor in the other direction.
- 144.6 — rounded an intermediate value before the final step.
Reference: FE Handbook — Euler's Equation
Euler's equation for a fluid particle in a converging nozzle Given pressure differential (dp) = -2,700 Pa; fluid density (rho) = 990.0 kg/m^3; velocity (V) = 2.8000 m/s; elevation differential (dz) = -0.2500 m; gravity (g) = 9.8100 m/s^2, determine the velocity differential (dV) in m/s.
Given
Find
velocity differential (dV), in m/s
Start with the thinking
- The governing relation printed in this handbook section is Euler's equation.
- Everything except dV is given, so isolate dV 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.
- Euler's equation for inviscid flow along a streamline underlies derivation of the Bernoulli equation.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange the relation so that dV stands alone on the left-hand side.
Step 3 — List the givens: pressure differential (dp) = -2,700 Pa, fluid density (rho) = 990.0 kg/m^3, velocity (V) = 2.8000 m/s, elevation differential (dz) = -0.2500 m, gravity (g) = 9.8100 m/s^2.
Step 4 — Substitute the given values into the rearranged relation.
Step 5 — Evaluate:
Step 6 — Check: returning dV = 1.8499 m/s to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 3.6998 — kept a factor of two that cancels in the correct rearrangement.
- 0.9250 — dropped that same factor in the other direction.
- 2.0349 — rounded an intermediate value before the final step.
Reference: FE Handbook — Euler's Equation
Euler's equation used to derive pressure change along a pipeline Given pressure differential (dp) = 1,340 Pa; fluid density (rho) = 860.0 kg/m^3; velocity (V) = 4.3000 m/s; velocity differential (dV) = 0.3000 m/s; gravity (g) = 9.7800 m/s^2, determine the elevation differential (dz) in m.
Given
Find
elevation differential (dz), in m
Start with the thinking
- The governing relation printed in this handbook section is Euler's equation.
- Everything except dz is given, so isolate dz 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.
- Euler's equation for inviscid flow along a streamline underlies derivation of the Bernoulli equation.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange the relation so that dz stands alone on the left-hand side.
Step 3 — List the givens: pressure differential (dp) = 1,340 Pa, fluid density (rho) = 860.0 kg/m^3, velocity (V) = 4.3000 m/s, velocity differential (dV) = 0.3000 m/s, gravity (g) = 9.7800 m/s^2.
Step 4 — Substitute the given values into the rearranged relation.
Step 5 — Evaluate:
Step 6 — Check: returning dz = -0.2912 m to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- -0.5824 — kept a factor of two that cancels in the correct rearrangement.
- -0.1456 — dropped that same factor in the other direction.
- -0.3203 — rounded an intermediate value before the final step.
Reference: FE Handbook — Euler's Equation
Euler's equation applied along a streamline in an accelerating flow Given fluid density (rho) = 1,020 kg/m^3; velocity (V) = 3.2000 m/s; velocity differential (dV) = 0.3900 m/s; elevation differential (dz) = 1.7500 m; gravity (g) = 9.7800 m/s^2, determine the pressure differential (dp) in Pa.
Given
Find
pressure differential (dp), in Pa
Start with the thinking
- The governing relation printed in this handbook section is Euler's equation.
- Everything except dp is given, so isolate dp 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.
- Euler's equation for inviscid flow along a streamline underlies derivation of the Bernoulli equation.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange the relation so that dp stands alone on the left-hand side.
Step 3 — List the givens: fluid density (rho) = 1,020 kg/m^3, velocity (V) = 3.2000 m/s, velocity differential (dV) = 0.3900 m/s, elevation differential (dz) = 1.7500 m, gravity (g) = 9.7800 m/s^2.
Step 4 — Substitute the given values into the rearranged relation.
Step 5 — Evaluate:
Step 6 — Check: returning dp = -18,730 Pa to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- -37,461 — kept a factor of two that cancels in the correct rearrangement.
- -9,365 — dropped that same factor in the other direction.
- -20,603 — rounded an intermediate value before the final step.
Reference: FE Handbook — Euler's Equation
Euler's equation for a fluid particle in a converging nozzle Given pressure differential (dp) = 270.0 Pa; fluid density (rho) = 1,050 kg/m^3; velocity (V) = 2.2000 m/s; elevation differential (dz) = 0.8000 m; gravity (g) = 9.7200 m/s^2, determine the velocity differential (dV) in m/s.
Given
Find
velocity differential (dV), in m/s
Start with the thinking
- The governing relation printed in this handbook section is Euler's equation.
- Everything except dV is given, so isolate dV 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.
- Euler's equation for inviscid flow along a streamline underlies derivation of the Bernoulli equation.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange the relation so that dV stands alone on the left-hand side.
Step 3 — List the givens: pressure differential (dp) = 270.0 Pa, fluid density (rho) = 1,050 kg/m^3, velocity (V) = 2.2000 m/s, elevation differential (dz) = 0.8000 m, gravity (g) = 9.7200 m/s^2.
Step 4 — Substitute the given values into the rearranged relation.
Step 5 — Evaluate:
Step 6 — Check: returning dV = -3.6514 m/s to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- -7.3029 — kept a factor of two that cancels in the correct rearrangement.
- -1.8257 — dropped that same factor in the other direction.
- -4.0166 — rounded an intermediate value before the final step.
Reference: FE Handbook — Euler's Equation
Euler's equation used to derive pressure change along a pipeline Given pressure differential (dp) = 4,610 Pa; fluid density (rho) = 1,200 kg/m^3; velocity (V) = 3.7000 m/s; velocity differential (dV) = -0.1800 m/s; gravity (g) = 9.8200 m/s^2, determine the elevation differential (dz) in m.
Given
Find
elevation differential (dz), in m
Start with the thinking
- The governing relation printed in this handbook section is Euler's equation.
- Everything except dz is given, so isolate dz 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.
- Euler's equation for inviscid flow along a streamline underlies derivation of the Bernoulli equation.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange the relation so that dz stands alone on the left-hand side.
Step 3 — List the givens: pressure differential (dp) = 4,610 Pa, fluid density (rho) = 1,200 kg/m^3, velocity (V) = 3.7000 m/s, velocity differential (dV) = -0.1800 m/s, gravity (g) = 9.8200 m/s^2.
Step 4 — Substitute the given values into the rearranged relation.
Step 5 — Evaluate:
Step 6 — Check: returning dz = -0.3234 m to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- -0.6468 — kept a factor of two that cancels in the correct rearrangement.
- -0.1617 — dropped that same factor in the other direction.
- -0.3557 — rounded an intermediate value before the final step.
Reference: FE Handbook — Euler's Equation
Euler's equation applied along a streamline in an accelerating flow Given fluid density (rho) = 1,060 kg/m^3; velocity (V) = 3.4000 m/s; velocity differential (dV) = -0.0300 m/s; elevation differential (dz) = -0.1000 m; gravity (g) = 9.7700 m/s^2, determine the pressure differential (dp) in Pa.
Given
Find
pressure differential (dp), in Pa
Start with the thinking
- The governing relation printed in this handbook section is Euler's equation.
- Everything except dp is given, so isolate dp 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.
- Euler's equation for inviscid flow along a streamline underlies derivation of the Bernoulli equation.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange the relation so that dp stands alone on the left-hand side.
Step 3 — List the givens: fluid density (rho) = 1,060 kg/m^3, velocity (V) = 3.4000 m/s, velocity differential (dV) = -0.0300 m/s, elevation differential (dz) = -0.1000 m, gravity (g) = 9.7700 m/s^2.
Step 4 — Substitute the given values into the rearranged relation.
Step 5 — Evaluate:
Step 6 — Check: returning dp = 1,144 Pa to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 2,287 — kept a factor of two that cancels in the correct rearrangement.
- 571.9 — dropped that same factor in the other direction.
- 1,258 — rounded an intermediate value before the final step.
Reference: FE Handbook — Euler's Equation