Question

When small particles of diameter d are transported by a moving fluid with velocity v, where do they settle to the ground?

a) At the starting point
b) At the source of the fluid
c) At some distance l
d) Immediately upon entering the fluid

Answer 1

Small particles settle to the ground at some distance from the starting point due to their terminal velocities and the velocity of the fluid.

Step-by-step explanation:

The settling of small particles transported by a moving fluid with velocity v depends on various factors, including the size of the particle and the velocity of the fluid. According to Stokes' law, smaller particles or particles with lower terminal velocities tend to settle more slowly than larger particles or particles with higher terminal velocities.

So, in this case, the small particles with diameter d would settle to the ground at some distance l from the starting point, option c. This distance depends on the terminal velocity of the particles and the velocity of the fluid.

For example, microorganisms, pollen, and dust particles are small particles that travel unaided at a constant (terminal) velocity. These particles settle to the ground at some distance from the starting point, typically taking days to reach the bottom of a lake or being deposited on the surface of a fluid.