But since they have nowhere to go sideways because of the walls of the dance hall, they just sit there getting squished. They quiver and shake from the load and the ones on the bottom are bearing all the weight of each layer of dancers above them. We drop a sphere of solid lead on top of the crowd, does it float on top? No, it is denser than the dancers and pushes them all out of the way while falling to the floor, and the dancers float instead (not a perfect analogy, but I think you get the picture).įinally: imagine we make a pyramid of the dancers on their hands and knees, with other dancers on top of them, and still more on top of them. We drop a big balloon on top of the crowd, does it fall to the floor? No, there are dancers in the way, and they are denser than the balloon so gravity pulls the dancers down and the balloon floats on top. The dancers are not holding hands, which means that they do not support shear forces, so they can slide past each other without much resistance. At any given instant, some are moving really fast, others more slowly, but on average they are all in rapid motion, moving only a tiny bit between collisions while all jammed together shoulder-to-shoulder.īecause their motion is random, as a group they don't go anywhere, but by slipping and sliding and squeezing about and swapping positions, each one will over time find itself drifting off away from its original position and in this manner the dance floor is well-mixed: none of them stick with their original dance partners for very long. They bounce off the walls and off of each other with equal force. Liquid molecules (taking water as an example) are constantly jostling about, bumping into, swapping places with, hitting head on, and squeezing past their neighbors like dancers in a mosh pit. Why don't liquid molecules move out to make way for the object, go to the side (while of course raising the height of the liquid) forming intermolecular bonds with new molecules as its moving to the side, as an object is submerged in them? What is the need of topic of buoyancy to explain fluid behavior when object are placed in them?įurthermore, if again as we all know if liquid molecules can glide past other other, why is pressure greater in the bottom of the container/ocean/lake than at the topic? Don't individual liquid particles glide past each other to move to the top and then come to the bottom all the time, thus (as you imagine millions of other individual molecules doing this also) equalizing pressure through the container? Thank you. For instance, if liquid particles can glide past each other, why do every object irrespective of their density not sink to the bottom of the container or floor of ocean/lake all the time. The reason why I ask this question is becasue I have difficulty understanding concepts like pressure, buoyancy, velocity. Like do individuals liquid molecules ever translate or glide past each other (and as they do so, keep creating temporary intermolecular bonds with other molecules) to the point that they travel from bottom of container to top, or from one lateral side of container/open ocean or lake to opposite side of container/open ocean or lake. I know that liquid molecules feel some sort of intermolecular attraction that is greater than that felt by solids but lower than that felt by gas molecules, which is the reason why liquids have definite volume unlike gas molecules.īut even with this fact, I have trouble imaging the journey of individuals liquid molecules, as they exist in a container or open lake, ocean together with millions of other molecules. I have tough time envisioning how if one were to follow a particular individual liquid particle in its journey and interaction with other liquid molecules in a given container, how it would actually behave.įor instance, I know the general facts like compared to in solids, molecules in liquids are free to not only vibrate from their mean position but also translate and slide past one another. I am trying to understand the concept of fluid pressure and its relation to fluid flow, velocity, buoyancy but in my attempt to understand these subtopics, I realize that my understanding of the movement/behavior of liquid molecules at a microscopic level is a bit lacking. I have just begun learning the topic of fluids in physics.
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