The opening near the bottom of the vessel has an area A. A disc is held against the opening to keep the liquid from running out. Let $$F1$$ be the net force on the disc applied by liquid and air in this case. Now the disc is moved away from the opening a short distance. The liquid comes out and strikes the disc in elastically. Let $$F2$$ be the force exerted by the liquid in this condition. Then, $$F1/F2$$ is:

Question

The opening near the bottom of the vessel has an area A.  A disc is held against the opening to keep the liquid from running out. Let $$F1$$  be the net force on the disc applied by liquid and air in this case. Now the disc is moved away from the opening a short distance. The liquid comes out and strikes the disc in elastically. Let $$F2$$  be the force exerted by the liquid in this condition. Then, $$F1/F2$$  is:

Infinity Learn · Accepted Answer

Let ρ      be the density of  liquid. Then,  $$F1=($$Δ$$P)A=$$ρgh A      …(1)     In the second case,$$F2=$$     rate of change of $$momentum=$$ρ$$Av2=$$ρ$$A(2gh)2$$     $$=2$$ρghA      …(2)     ∴      $$F1F2=12$$

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