It is required to lift a granite stone with a volume of 25,000 cm3 from the bottom of the river. What force should be applied for this?

To find the force that will need to be applied to a given stone, we apply the formula: F = Fт – Fа = m * g – ρрв * g * V = ρгк * V * g – ρрв * g * V = V * g * (ρгк – ρрв ).

Values of variables: V – volume of granite stone (V = 25000 cm3 = 0.025 m3); g – acceleration due to gravity (g ≈ 10 m / s2); ρгк – density of a granite stone (ρгк = 2600 kg / m3); ρрв – density of river water (ρрв = 1000 kg / m3).

Calculation: F = V * g * (ρгк – ρрв) = 0.025 * 10 * (2600 – 1000) = 400 N.

Answer: A force of 400 N must be applied to a given stone.