How it works
Use stokes sphere settling with the units stated beside the fields. This form solves for speed; enter the known quantities in Radius, Local gravitational acceleration, Sphere density, Fluid density, Dynamic viscosity.
Inputs and units
| Input | Example value | What to enter |
|---|---|---|
| Radius | 0.00075 m | Formula symbol: r. Required unit: m. Distance from the centre to the edge; half the diameter. Must be greater than zero. |
| Local gravitational acceleration | 7.5 m/s² | Formula symbol: g. Required unit: m/s². Must be greater than zero. |
| Sphere density | 900 kg/m³ | Formula symbol: ρₚ. Required unit: kg/m³. Must be greater than zero. |
| Fluid density | 750 kg/m³ | Formula symbol: ρ𝒻. Required unit: kg/m³. Must be greater than zero. |
| Dynamic viscosity | 0.75 Pa·s | Formula symbol: μ. Required unit: Pa·s. Must be greater than zero. |
Worked example
Show example inputs and results
This example is generated by the same calculation engine using the starting values in the form. Your own inputs produce your own result.
- Radius
- 0.00075 m
- Local gravitational acceleration
- 7.5 m/s²
- Sphere density
- 900 kg/m³
- Fluid density
- 750 kg/m³
- Dynamic viscosity
- 0.75 Pa·s
Complete example results
- Speed
- 0.0001875 m/s
Reading the result
The result solves for speed from the entered quantities. Check the result unit and the formula conditions before using it.
Questions and answers
Can I use the example values for my own calculation?
The example values illustrate the calculation. Replace every input with your own information, especially dates, rates and the selected operation.
When can I use the speed result?
This model uses positive magnitudes. An isolated sphere is denser than the fluid and at terminal speed, without wall effects. This tool limits diameter-based Reynolds number below 0.1; higher-Reynolds or transient falling is excluded.
Why are some results rounded?
Results display up to 8 decimal places. Calculations use the unrounded values; very small values use scientific notation. JavaScript floating-point arithmetic can introduce tiny rounding differences.
Are my inputs sent to a server?
The calculator processes inputs in your browser. Its code does not send your values to a server.
Method sources: openstax.org