Question

calculate the weight of a stone of mass 10 kg and density 10000kg/m³ when it is totally immersed in water

Answer 1

the stone is ten times as dense as water
... so it will displace one tenth of its weight in water

w = m * g * .9

Answer 2

D = M/V
10,000 = 10/V
V = 0.001 m^3. = vol. of stone = vol. of water disp.

D = M/V
1000 = M/0.001
M = 1 kg = mass of water disp. = mass lost by stone.
M*g = (10-1)*9.8 = 88.2 N. = Wt. of stone when tot. immersed.