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If a water pump is placed at the bottom of a container and used to fill the container it would need to pump against the pressure of standing water. If a weighted object is floated on the surface of the same water within the container, is the pump required to work harder to fill the container? Is there an equation I can use to calculate the differance in pumping pressure in both situations? Thanks

Point 2: Looking at the image below is there an equation which states the pump power (CBM/s) based on the weight of object X, Float Y, and the amount of water in the tank CBM? To put this into context the weight (in this case X) would be a concrete basin filled with soil sitting on top of a floating pontoon (Y) inside a concrete basin. The pump would push water below the basin lifting it up (by a height of around 5-10m. The calculation needs to take account of the size of the basin which could be built according to the specifications.

enter image description here

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If the tank is open at the top, so air pressure above the water does not increase as the water rises, then the pressure at the bottom will increase as the water level increases. This pressure is about 1.47 psi for each meter below the water surface. A buoyant object will sink into the water until the water displaced equals it's weight, then it will float partially submerged. The water level will rise from the object's water displacement, increasing the amount of pressure at the bottom. Say the object were big enough to raise the water level 1 meter, the pressure at the bottom would increase another 1.47 psi.

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  • $\begingroup$ Thanks Adrian. I have slightly modified the question to add some context. Does the same rule still apply? $\endgroup$ Nov 11, 2019 at 12:42
  • $\begingroup$ If you are talking about something floating in water then yes, if you mean a piston in a cylinder pushing water that is different. $\endgroup$ Nov 11, 2019 at 13:01

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