Buoyancy and Archimedes' Principle MCQs

Q1. A goldsmith checks an ornament: it weighs 45 N in air and 41 N when hung in water. What is the relative density (specific gravity) of the material?

• A.1.0976
• B.11.25
• C.0.0889
• D.10.25

Answer: B. 11.25

Loss of weight in water = 45 - 41 = 4 N (= weight of displaced water). Relative density = weight in air / loss of weight = 45 / 4 = 11.25.

Q2. To test a coin a student finds its weight is 30 N in air but only 24 N submerged in water. What is the relative density (specific gravity) of the material?

• A.4
• B.0.2
• C.5
• D.1.25

Answer: C. 5

Loss of weight in water = 30 - 24 = 6 N (= weight of displaced water). Relative density = weight in air / loss of weight = 30 / 6 = 5.

Q3. A curator records that an artefact weighs 25 N dry and 15 N while fully under water. What is the relative density (specific gravity) of the material?

• A.1.6667
• B.2.5
• C.0.4
• D.1.5

Answer: B. 2.5

Loss of weight in water = 25 - 15 = 10 N (= weight of displaced water). Relative density = weight in air / loss of weight = 25 / 10 = 2.5.