Factors Influencing Particle Motion in a Stream:
* Particle Density: A denser particle requires a stronger force (and thus higher velocity) to keep it moving.
* Stream Density: The density of the fluid (water, air, etc.) plays a role. A denser fluid provides more resistance.
* Particle Shape: A smooth, spherical particle will be easier to move than an irregularly shaped one.
* Stream Turbulence: Turbulence will contribute to particle movement, potentially requiring a lower average velocity.
* Streambed Roughness: A rough bed will increase friction, potentially requiring a higher velocity.
* Particle Settling Velocity: This is the rate at which a particle falls in still water. It's a crucial factor in determining the minimum velocity needed to prevent settling.
How to Approach the Problem:
1. Identify the Fluid: Is the stream water, air, or another fluid?
2. Determine Particle Density: What is the density of the particle material?
3. Consider Shape and Roughness: Is the particle smooth or rough? Is the streambed smooth or rough?
Using the Hjulström Curve:
Once you have that information, you can use a tool like the Hjulström Curve. This curve helps visualize the relationship between particle size, stream velocity, and erosion, transport, and deposition. However, it's important to note that the Hjulström Curve is a generalization and may not be perfectly accurate for every scenario.
Example:
If you're dealing with a 10 cm diameter, relatively smooth, quartz particle in a river, you'd need to consider the density of quartz, the density of water, and the roughness of the riverbed. The Hjulström Curve would then give you a general idea of the minimum stream velocity needed to keep the particle in motion.
Conclusion:
Without additional information, providing an approximate minimum stream velocity is impossible. You need to consider the factors listed above to make an accurate assessment.
