WAEC SSCE - Physics - 2002 (Objective)

Question 1 Report

A solid weight 45N and 15N respectively in air and water. Determine the relative density of the solid

0.33

0.50

1.50

3.00

Answer Details

The relative density of a substance is defined as the ratio of its density to the density of a reference substance. In this case, the reference substance is water. When the solid is in air, it experiences a weight of 45N. This means that the weight of the displaced air is also 45N. Therefore, the density of the solid is: density of solid = weight of solid / volume of solid Since the volume of the solid is the same in air and in water, we can write: density of solid in air = weight of solid / volume of solid = weight of displaced air / volume of solid When the solid is in water, it experiences a weight of 15N. This means that the weight of the displaced water is 45N - 15N = 30N. Therefore, the density of the solid is: density of solid in water = weight of solid / volume of solid = weight of displaced water / volume of solid Now, the relative density of the solid is defined as the ratio of the density of the solid to the density of water: relative density of solid = density of solid / density of water We can substitute the expressions we obtained for the densities of the solid in air and in water: relative density of solid = (weight of displaced air / volume of solid) / (weight of displaced water / volume of solid) Simplifying this expression, we get: relative density of solid = weight of displaced air / weight of displaced water Substituting the values we obtained for the weights of displaced air and water, we get: relative density of solid = 45N / 30N = 1.5 Therefore, the relative density of the solid is 1.5. Answer: 1.50






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