Question

The weight of a lead sinker was found to be 42 g. A graduated cylinder was filled with 50 ml of water. When the lead sinker was dropped into the cylinder, the water level rose to 64 ml. Calculate the specific gravity of the sinker.

Answer 1

The formula for calculating the specific gravity of an object using water as reference is to divide the Density of Object by the density of water.

Now we know that the density of water is 1 gram/cm3 but we do not know the density of the Sinker.

This is where the water displacement method comes in handy. Density can be found by dividing the Mass by volume. Now, the mass is 42gm while volume is equal to the increase in water level.

According to the question, water was at 50 ml but increased to 64 ml. Thus the displacement is by 14 ml (64 ml - 50 ml). Thus the volume is 14 cm3. This is because 1 ml equals to 1 cm3.

Now, density of sinker = 42/14 = 3.

So the density of sinker is 3gm/cm3.

Specific gravity = Density of sinker/density of water.

3 / 1 = 3.

This means that the specific gravity of sinker is 3.