A boat floating in a water tank is carrying a number of large stones. If the stones are unloaded into water, what will happen to the water level?

Explanation

Let `M` : mass of boat,
`m` : total mass of stone pieces
For floatation `(M + m)g= rho_omega V g`
`V = (M + m)/(rho_omega) = (M)/(rho_omega) + (m)/(rho_omega)`
`V` : volume of water displaced
Now stones are unloaded into water, stone sinks.
The volume of water displaced
`V' = (M)/(rho_omega) + (m)/(rho_s)`
`rho_s gt rho_omega`
`(m)/(rho_s) lt (m)/(rho_omega)`
`((M)/(rho_omega) + (m)/(rho_s)) lt ((M)/(rho_omega) + (m)/(rho_omega))`
`V' lt V`
The level of water goes down.