question_answer

         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:

                  Actually mass of cotton is more than the mass of iron bar. This is because Weight measured = Actual weight - buoyant force Actual weight = weight measured + buoyant force The volume of cotton is much more than the volume of iron bar, so buoyant force (B = volume of object x density of air x g) of air on cotton is much more than that of air on iron bar, so mass of cotton will be more than the mass of iron bar.