∴ water quality m water = rho water v water =1.0×103kg/m3× 500× 6mm 3 = 0.5kg,

Pressure of bottle on sponge:

F=G water +G bottle =m water g+G bottle = 0.5kg× 9.8n/kg+1.1n = 6n,

The pressure of the bottle on the sponge p = fs6n0.002m2 = 3000pa.

(2) In order to make the pressure on the sponge equal when the bottle is inverted and upright,

When the bottle is inverted, a piece of cardboard with an area of 0.002m2 can be placed under it.

Answer: (1) The pressure of pure water on sponge is 3000Pa. ..

(2) When the bottle is upside down, put cardboard with an area of 0.002m2 under it.