The answer is 2,646 N
(see Page 90 - section 5 example)
F=Veg
F= 0.09 m3 x 4,000 kg/m3 x 9.8 m/s2
F= 360 x 9.8
F = 3,528 ( this is the force of gravity acting on the block in air)
What is the force of gravity acting on the block in water:
F=mg
F= Vdg
F= 0.09 m3 x 1,000 kg/m3 x 9.8 m/s2
F= 90 x 9.8
F= 882 N
subtract the weight of the displaced water from 3,528 N
(3,528 N - 882 N = 2,646 N)
The force of gravity acting on the block in water is 2,646 N