Row v = v = 3x10-3m3,
Buoyancy of buoy p:
F float = ρ water gv row =1.0×103kg/m3×10n/kg× 3×10-3m3 = 30n;
(2)∫f floating =gp+f pulling force
∴f pulling force =f floating-gp = 30n-0.4kg×10n/kg = 26n;
(3) The cover Q has just been pulled open,
∴g cover +f pressure =f tension =26n,
F pressure =f tension -g cover =26n-0.2kg× 10n/kg=24n,
F pressure = PS = rhoghs,
∴h=
F pressure
ρgs
=
24n
1000kg/m3× 10n/kg×8× 10? 3 square meters
=0.3m。
Answer: (1) The buoyancy on the buoy is 30n;;
(2) The pulling force of the thin line on the buoy P is 26n;;
(3) The water depth in the water tank is 0.3m. 。