WEIGHT (W):The weight of an object is defined as the force of gravity on the object and may be calculated as the mass times the acceleration of gravity, i.e.,W = mgWhere m = mass of the object and g = acceleration due to gravitySince the weight is a force, its SI unit is the Newton.Archimedes principle:The principle of Archimedes states “When a body is immersed in a liquid, an upward thrust, EQUAL to the weight of the liquid displaced, acts on it.”Thus, when a solid is FULLY immersed in a liquid, it loses weight which is equal to the weight of the liquid it displaces.Apparent weight = Actual weight - Buoyant force = mg - ρgVWhere m is mass of the object, ρ is the density of the fluid, V is submerged volume.Calculation:Given:The apparent weight of an object in water = 50 N, V = 15.3 litre = 15 × 10-3 m3, specific gravity of oil = 0.8 or density of oil = 800 kg/m3Actual weight of the object = The apparent weight of the object in water = Actual weight - Buoyant force by waterρogV - ρwgV = 50 = gV (ρo - ρw)10 × 15 × 10-3 × (ρo - 1000) = 50ρo = 1326 kg/m3The apparent weight of the object in oil = Actual weight - Buoyant force by oilThe apparent weight of the object in oil = ρogV - ρoilgV =gV × (ρo - ρoil) = 10 × 15.3 × 10-3 × (1326 - 800) = 80.47 N