cougarmeat
Paddler
As my partner’s granddaughter is now tall enough to assist at the kitchen sink, I can show her the fun of sinking the floating dishes at wash time. I’ll try to do it without militaristic overtones (or humming the “Sink the Bismark” song). And I was thinking of explaining that if something is lighter than the water it displaces, it will float - Right? Do I understand that correctly? We could experiment by weighing things and weighing the water they displace.
But other scenarios came to mind and I’m trying to make them gel with that displacement statement. Like I can float in water when I have a deep breath. But when I exhale, I sink. Because I’m not changing my weight - I do exhale when on the scale for my yearly physical but it doesn’t seem to affect the reading much - I imagine the inhale, expanding the lungs, creates a larger “body” that displaces more water.
Then I thought about being vertical in the water and how I go to the bottom (same volume displacement) but in that case I’m not “neutral”. Like I can put a stick vertically in the water but if no other forces are on it, it will “adjust” to the position it needs to float. So I’d image I’d float too if I didn’t try to influence body position.
The stumper is when something floats partially submerged - like “floating” a few feet under the surface. Can logs do that? Or submarines? I can see how a submarine can travel at X depth when moving because the vanes can act on the water while the boat is moving forward. But just hovering at a certain depth? It seems the volume displaced - the outside of surface of the submarine is the same. As ballast is let in, the boat becomes heavier than the volume the hull displaces so it dives.
The part I am missing is this displacement idea seems to be, “It floats or it sinks.” What needs to be added is an explanation of why something doesn’t float on the surface, or sink to the bottom. Perhaps it has to something to do with water pressure pushing up from below vs the water above the submarine (or body, or log) pushing down from above?
What am I missing?
But other scenarios came to mind and I’m trying to make them gel with that displacement statement. Like I can float in water when I have a deep breath. But when I exhale, I sink. Because I’m not changing my weight - I do exhale when on the scale for my yearly physical but it doesn’t seem to affect the reading much - I imagine the inhale, expanding the lungs, creates a larger “body” that displaces more water.
Then I thought about being vertical in the water and how I go to the bottom (same volume displacement) but in that case I’m not “neutral”. Like I can put a stick vertically in the water but if no other forces are on it, it will “adjust” to the position it needs to float. So I’d image I’d float too if I didn’t try to influence body position.
The stumper is when something floats partially submerged - like “floating” a few feet under the surface. Can logs do that? Or submarines? I can see how a submarine can travel at X depth when moving because the vanes can act on the water while the boat is moving forward. But just hovering at a certain depth? It seems the volume displaced - the outside of surface of the submarine is the same. As ballast is let in, the boat becomes heavier than the volume the hull displaces so it dives.
The part I am missing is this displacement idea seems to be, “It floats or it sinks.” What needs to be added is an explanation of why something doesn’t float on the surface, or sink to the bottom. Perhaps it has to something to do with water pressure pushing up from below vs the water above the submarine (or body, or log) pushing down from above?
What am I missing?