With what force the oil presses on the crane, the area of which is 8 cm (2) at a depth of 4 meters.

To find the force of oil pressure on the valve under consideration, we use the formula: F = P * S = ρн * g * h * S.

Variables and constants: ρн – oil density (ρн = 800 kg / m3); g – acceleration due to gravity (g ≈ 10 m / s2); h is the height of the oil column above the crane (h = 4 m); S – tap area (S = 8 cm2 = 8 * 10 ^ -4 m2).

Let’s make a calculation: F = ρн * g * h * S = 800 * 10 * 4 * 8 * 10 ^ – 4 = 25.6 N.

Answer: Oil presses on the valve under consideration with a force of 25.6 N.