- #1

- 1

- 0

So, I know that Pascal's principle underlies the workings of the hydraulic lift, and I know that while force is multiplied on the piston/platform with larger area, the distance moved relative to the smaller piston/platform is inversely proportional to the increase in force. What I'm not quite understanding is why in this case the ratio of the areas affects the distance the fluid is raised, while in the case of, say, a mercury barometer the ratio of the area of the reservoir to the area of the tube is not relevant to the distance the fluid in the tube is raised, and only the pressure difference is. I've found a lot of resources that say THAT this is the case, just not any that explain why.

Tangentially, to the degree that comfort in bedding is related to pressure on the body (not the only factor, obviously, but a significant one), wouldn't Pascal's principle indicate that air/water beds would be among the least comfortable sleeping surfaces, since the pressure applied by the densest areas of the anatomy would be transmitted largely undiminished across the surface of the container? I often hear it said by people who market air/water beds that they "redistribute" pressure, but as I understand Pascal's principle, they definitely don't redistribute pressure (in the sense in which if you had 2 equal areas of the body that would otherwise have, say, 40 mmHg and 20 mmHg of pressure applied to them, they instead have 30 mmHg applied across the combined surface). Instead, it seems they would take the worst pressure point and apply that pressure across the entire surface. Is there something I'm completely misunderstanding here (I imagine there is, but I'm not sure what it is)?

I realize the first question is probably really basic, and that the second is probably really basic and a little odd, but I couldn't think of a better place to ask these questions. I apologize if there's a better place I should be asking these questions, and I thank you in advance for any attempts to help!