Fluid Properties MCQ with answer and solution

Concept

Specific gravity is the density of a liquid divided by the density of water.

Formula

w = W/V, ρ = w/g, S = ρ_oil/ρ_water

Step-by-step solution

1. Volume V = 2 litres = 2 × 10^-3 m³ = 0.002 m³ 2. Specific weight w = W/V = 16/0.002 = 8000 N/m³ 3. Density of oil ρ_oil = w/g = 8000/9.81 = 815.5 kg/m³ 4. Specific gravity S = ρ_oil/ρ_water = 815.5/998 = 0.817 5. Nearest option is 0.816, so the answer is (B)

Explanation

First find the weight per unit volume of the oil, then divide by g to get its density. Divide this density by the density of water (998 kg/m³) to get the specific gravity, which is about 0.817, nearest to 0.816.

Why the other options are wrong

A) 0.846, C) 0.856 and D) 0.786 do not match the calculated value of about 0.817.

Shortcut

S = W/(V × ρ_water × g) = 16/(0.002 × 998 × 9.81) ≈ 0.817

Common mistake

Forgetting to convert litres to m³ (1 litre = 10^-3 m³), or using 1000 kg/m³ instead of the given 998 kg/m³.