(2011? Chongqing) In the construction of new rural areas, many buildings are equipped with solar water heaters on their roofs. The picture below is a schematic diagram of the structure of the internal

(2011? Chongqing) In the construction of new rural areas, many buildings are equipped with solar water heaters on their roofs. The picture below is a schematic diagram of the structure of the internal water tank. Sl is automatic temperature control

(1) Heat absorbed by water:

Q absorption=cm△t=4.2×103J/(kg?℃)×100kg×20℃=8.4×106J;

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(2)G total=m total g=ρV total g=ρ(VA+VB)g=1.8×103kg/m3×(5×10-4m3+5×10-4m3)×10N/kg =18N,

(3) Under normal circumstances, when the water level is the highest, the tension on the rope is the smallest. At this time,

F total float =G total-F=18N-10N= 8N

FB float=ρwater gVB=1.0×103kg/m3×5×10-4m3×10N/kg=5N

FA float=F total float-FB float=8N -5N=3N

Answer: (1) The heat absorbed by water is 8.4×106J;

(2) The volumes of A and B are both 500cm3, and the total gravity of A and B is 18N;

(3) Under normal circumstances, when the water level in the water tank is the highest, the buoyancy force on A is 3N.