A brick measuring 5 * 10 * 20cm is completely submerged in water. What force must be applied to lift it?

A brick in water is acted upon by the force of Archimedes and the force of gravity. These forces are exactly the opposite.
Р = mg – ρgV, where m is the mass of the brick (m = ρк * V, where ρк is the density of the brick (for solid bricks, the average density is ρк = 1750 kg / m ^ 3, V is the volume of the brick (V = 0.05 * 0 , 1 * 0.2 = 0.001 m ^ 3))), g is the acceleration of gravity (g = 10 m / s ^ 2), ρ is the density of water (ρ = 1000 kg / m ^ 3).
Р = mg – ρgV = ρк * V * g – ρgV = 1750 * 0.001 * 10 – 1000 * 10 * 0.001 = 17.5 – 10 = 7.5 N
Answer: To lift a brick, a force of 7.5 N is required.