Question

A physics student looks into a microscope and observes that small particles suspended in water are moving about in an irregular motion. Which of the following statements is the best explanation for this observation?
a. water molecules strike the particles giving them the same average kinetic energy as the water
b. the particles are carried by convection currents in the water
c. the small particles may be considered a fluid; and thus, move about randomly
d. the actual motion is regular, but the speeds of particles are too large to observe the regular motion
e. the particles are moving to be uniformly distributed throughout the volume of the water

Answer 1

Answer:

d. the actual motion is regular, but the speeds of particles are too large to observe the regular motion

Explanation:

The speeds of the particles are very large and comparatively the average  free path is very small . Therefore time taken in covering the free path ( path between two consecutive collision with medium particles ) is very small . Hence the st line  path covered by particles between two collision is less likely to be visible. Hence motion appears irregular or zig-zag.