Question 2491 Deck Safety

The correct answer is B) .33 feet. The reduction in GM due to free surface effect is calculated using the formula: Reduction in GM = (I / ΔR), where I is the moment of inertia of the free surface and ΔR is the vessel's displacement. In this case, the moment of inertia of the free surface is calculated as I = (1/12) * (20 ft)^3 * 2 = 8,000 ft^4, since each tank is 20 ft wide and 60 ft long, and there are two tanks. The vessel's displacement is given as 7,000 tons, which is equivalent to 218,000 ft^3. Plugging these values into the formula, the reduction in GM is calculated as (8,000 ft^4 / 218,000 ft^3) = 0.33 feet, which corresponds to answer choice B. The other answer choices are incorrect because they do not correctly apply the formula for calculating the reduction in GM due to free surface effect.