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 the other. Can you say which one is heavier and why?

Answer 1

The cotton bag is more heavier than the iron bar

• The true weighht of the body also depends on the upthrust force on the body

    True weight = Apparent weight + Upthrust force

• The cotton bag has more volume due to less density of cotton compared to iron bar

• Due to more volume in case of cotton bag the upthrust force on the cotton bag due to air is more

• So the cotton bag will have more weight than the iron bar

Answer 2

The cotton bag's density is less than that of the iron bar, so the volume of the cotton bag is more compared to the iron bar. So the cotton bag experience more upthrust due to the presence of air. Therefore, in the presence of air, the cotton bag's true weight is more compared to the true weight of the iron bar.

Hope it helps you