Yichang u photography

(1) The internal pressure of water is converted into the liquid level difference on both sides of the U-shaped pipe to judge. Xiao Ming increases the depth of the metal box in the water, and the liquid level difference is also greater, indicating that the internal pressure of water is greater.

(2) To explore the relationship between liquid pressure and liquid density, the probe of the pressure gauge should be at the same depth of different liquids.

(3) Let the height of the liquid column model in Figure B be H, the liquid film area under the liquid column be S, and the liquid column density be ρ;

Steps: ① The volume of this liquid column v = sh.

② The mass of this liquid column m =ρV =ρSH；;

(3) The gravity of this liquid column is the pressure on the horizontal plane F = G = Mg = ρ GSH;

(4) pressure on the plane p = fs = rhogshs = rhogh.

Therefore, the pressure of liquid at depth h is p = ρ GH.

So the answer is: (1) The deeper the metal box is immersed in water, the greater the height difference between the two sides of the U-shaped pipe; (2) The probe of pressure gauge should be at the same depth of different liquids; (3) The derivation process is the same as above.