2. A cube made of a material with a density $\rho_{1}$, which is 3 times the density of water $\rho_{0}$, is located at the bottom of a container filled with water. With what acceleration and in what direction should the container be moved to make the cube start to float?
Answer: no less than $g$ downward. Solution. If the acceleration of the vessel is greater than or equal to $\mathrm{g}$, the pressure of the column on the upper surface of the cube is absent. Since the reaction force of the vessel is directed upward or is zero, the acceleration of the cube relative to the ground does not exceed $\mathrm{g}$, and the relative acceleration will be directed upward, that is, the cube will begin to float.