Question

You have a bag of cotton and an iron bar, each indicating a mass of 100 kg when measured on a weighing machine. In reality, one is heavier than other. Can you say which one is heavier and why?

Answer 1

• The cotton bag is heavier than the iron bar because the cotton bag's surface area is larger than that of the iron bar.
• Hence, more buoyant force acts on the bag than on an iron bar, making the cotton bag heavier than its actual value.
• For this reason, the iron bar and the cotton bag show the same mass on the weighing machine, but the mass of the cotton bag is greater than that of the iron bar.
• Actual weight = Measured Weight + Buoyant Force