Answer:
Upper scale reads 4.4kg while lower scale reads 7.6 kg
Explanation:
The buoyant force of the water on the aluminum piece would equal to the weight of the water displaced by the aluminum.
The mass of the water displaced by aluminum is
[tex]m_w = V_w \rho_w = \frac{m_a}{\rho_a}\rho_w = \frac{7}{2700}1000 = 2.6 kg[/tex]
As 7kg aluminum piece is supported by 2.6 kg buoyant force, the scale that the aluminum is hung on would read
Mass of aluminum - mass of water displaced
7 - 2.6 = 4.4 kg
This buoyant force would also created a reaction on the lower scale of 2.6 kg (according to Newton's 3rd law). So the lower scale would read:
Mass of water + mass of bleak + mass of buoyant reaction force
3 + 2 + 2.6 = 7.6 kg
