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Game_Minds t1_j10yw5w wrote

Reply to comment by labroid in Could being submersed in a sealed tank of fluid help humans survive heavy G acceleration in outer space? by cheeze_whiz_shampoo

I think this, they would actually float 'up' in the direction of acceleration if there was a difference in density between the person and the water, because as the water experiences differential pressure the body might be able to maintain internal pressures. However, when the lowest pressure at any point in the tank is above a lethal amount it would still kill you. So at mega high accelerations you aren't safe even in a very large but not infinite tank

Edit: I think this is right. The acceleration of hitting the ground only kills you because it causes forces to act across your body unevenly very rapidly, g forces from acceleration work the same way. So if you don't implode from the pressure, you're still experiencing an acceleration difference across different parts of your body inhomogeneously because the actual thing keeping you intact in the water is your skin. You would still die of g forces suspended in a liquid

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labroid t1_j114f3e wrote

The person displaces their weight in water - that's the "on Earth" definition. The more general definition is they displace their mass. Their weight is m * a and the water they displace is rho * V * a (rho is density, V is volume, and a is acceleration). Where you float is therefore

m * a = rho * V * a

So you cancel the a on both sides and get

m = rho * V

(for fun note that rho * V is the mass of the water). So the general form of buoyancy is that you float where you displace your mass in water. Note this is completely independent on acceleration (g's). So the person will stay in the same position, unless compressed by the extra pressure of the pool, at which point they will "sink" (move in the direction of the acceleration vector). Of course getting compressed is the "then you die" part of the problem...

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Game_Minds t1_j120vu3 wrote

The fluids in a person's body have different densities at a given pressure

It would be like putting you in a centrifuge, some of your parts like your bones would have different buoyancy than others and would experience pressure to separate out

It would be significantly less pressure than other forces acting on you and it might be too small to overcome the forces your body exerts

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